1481 lines
46 KiB
Markdown
1481 lines
46 KiB
Markdown
## 1.1 今日目标
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1. 理解多表查询
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2. 理解子查询
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3. 能够创建视图
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4. 能够删除视图
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5. 能够查看创建视图的SQL语句
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6. 能够理解事务的作用
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7. 能够操作事务
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8. 理解索引的作用
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9. 能够创建索引
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10. 能够删除索引
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11. 知道常用的函数
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12. 了解预处理语句的作用
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13. 能够使用预处理语句
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14. 了解存储过程的作用
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15. 能够创建存储过程
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16. 能够调用存储过程
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## 1.2 多表查询分类
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将多个表的数据横向的联合起来。
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1、 内连接
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2、 外连接
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a) 左外连接
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b) 右外连接
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3、 交叉连接
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4、 自然连接
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#### 1.2.1 内连接【inner join】
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```
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语法一：select 列名 from 表1 inner join 表2 on 表1.公共字段=表2.公共字段
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语法二：select 列名 from 表1,表2 where 表1.公共字段=表2.公共字段
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```
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例题
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```sql
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方法一：
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mysql> select stuname,stusex,writtenexam,labexam from stuinfo inner join stumarks on stuinfo.stuno=stumarks.stuno;
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+----------+--------+-------------+---------+
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| stuname | stusex | writtenexam | labexam |
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+----------+--------+-------------+---------+
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| 李斯文 | 女 | 80 | 58 |
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| 李文才 | 男 | 50 | 90 |
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| 欧阳俊雄 | 男 | 65 | 50 |
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| 张秋丽 | 男 | 77 | 82 |
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| 争青小子 | 男 | 56 | 48 |
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+----------+--------+-------------+---------+
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方法二：
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mysql> select stuinfo.stuno,stuname,stusex,writtenexam,labexam from stuinfo,stumarks where stuinfo.stuno=stumarks.stuno;
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+--------+----------+--------+-------------+---------+
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| stuno | stuname | stusex | writtenexam | labexam |
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+--------+----------+--------+-------------+---------+
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| s25303 | 李斯文 | 女 | 80 | 58 |
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| s25302 | 李文才 | 男 | 50 | 90 |
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| s25304 | 欧阳俊雄 | 男 | 65 | 50 |
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| s25301 | 张秋丽 | 男 | 77 | 82 |
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| s25318 | 争青小子 | 男 | 56 | 48 |
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+--------+----------+--------+-------------+---------+
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可以给表取别名
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mysql> select i.stuno,stuname,stusex,writtenexam,labexam from stuinfo i,stumarks s where i.stuno=s.stuno;
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+--------+----------+--------+-------------+---------+
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| stuno | stuname | stusex | writtenexam | labexam |
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+--------+----------+--------+-------------+---------+
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| s25303 | 李斯文 | 女 | 80 | 58 |
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| s25302 | 李文才 | 男 | 50 | 90 |
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| s25304 | 欧阳俊雄 | 男 | 65 | 50 |
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| s25301 | 张秋丽 | 男 | 77 | 82 |
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| s25318 | 争青小子 | 男 | 56 | 48 |
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+--------+----------+--------+-------------+---------+
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5 rows in set (0.00 sec)
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```
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脚下留心：显示公共字段需要指定表名 
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```
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思考：
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select * from 表1 inner join 表2 on 表1.公共字段=表2.公共字段 和
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select * from 表2 inner join 表1 on 表1.公共字段=表2.公共字段 结果是否一样？
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答：一样的，因为内连接获取的是两个表的公共部分
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```
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```
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多学一招：三个表的内连接如何实现？
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select * from 表1 inner join 表2 on 表1.公共字段=表2.公共字段
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inner join 表3 on 表2.公共字段=表3.公共字段
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```
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#### 1.2.2 左外连接【left join】
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以左边的表为标准，如果右边的表没有对应的记录，用NULL填充。
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```
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语法：select 列名 from 表1 left join 表2 on 表1.公共字段=表2.公共字段
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```
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例题
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```sql
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mysql> select stuname,writtenexam,labexam from stuinfo left join stumarks on stuinfo.stuno=stumarks.stuno;
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+----------+-------------+---------+
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| stuname | writtenexam | labexam |
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+----------+-------------+---------+
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| 张秋丽 | 77 | 82 |
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| 李文才 | 50 | 90 |
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| 李斯文 | 80 | 58 |
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| 欧阳俊雄 | 65 | 50 |
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| 诸葛丽丽 | NULL | NULL |
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| 争青小子 | 56 | 48 |
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| 梅超风 | NULL | NULL |
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+----------+-------------+---------+
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```
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```
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思考：
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select * from 表1 left join 表2 on 表1.公共字段=表2.公共字段
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和
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select * from 表2 left join 表1 on 表1.公共字段=表2.公共字段 是否一样？
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答：不一样，左连接一左边的表为准。
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```
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#### 1.2.3 右外连接【right join】
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以右边的表为标准，如果左边的表没有对应的记录，用NULL填充。
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```
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语法：select 列名 from 表1 right join 表2 on 表1.公共字段=表2.公共字段
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```
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例题
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```sql
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mysql> select stuname,writtenexam,labexam from stuinfo right join stumarks on stuinfo.stuno=stumarks.stuno;
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+----------+-------------+---------+
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| stuname | writtenexam | labexam |
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+----------+-------------+---------+
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| 李斯文 | 80 | 58 |
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| 李文才 | 50 | 90 |
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| 欧阳俊雄 | 65 | 50 |
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| 张秋丽 | 77 | 82 |
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| 争青小子 | 56 | 48 |
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| NULL | 66 | 77 |
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+----------+-------------+---------+
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6 rows in set (0.00 sec)
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```
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```
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思考：
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select * from 表1 left join 表2 on 表1.公共字段=表2.公共字段
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和
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select * from 表2 right join 表1 on 表1.公共字段=表2.公共字段 是否一样？
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答：一样的
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```
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#### 1.2.4 交叉连接【cross join】
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插入测试数据
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```sql
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mysql> create table t1(
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-> id int,
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-> name varchar(10)
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-> );
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Query OK, 0 rows affected (0.06 sec)
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mysql> insert into t1 values (1,'tom'),(2,'berry');
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Query OK, 2 rows affected (0.00 sec)
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mysql> create table t2(
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-> id int,
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-> score int);
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Query OK, 0 rows affected (0.02 sec)
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mysql> insert into t2 values (1,88),(2,99);
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```
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1、如果没有连接表达式返回的是笛卡尔积
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```sql
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mysql> select * from t1 cross join t2; # 返回笛卡尔积
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+------+-------+------+-------+
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| id | name | id | score |
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+------+-------+------+-------+
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| 1 | tom | 1 | 88 |
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| 2 | berry | 1 | 88 |
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| 1 | tom | 2 | 99 |
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| 2 | berry | 2 | 99 |
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+------+-------+------+-------+
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```
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2、如果有连接表达式等价于内连接
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```sql
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mysql> select * from t1 cross join t2 where t1.id=t2.id;
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+------+-------+------+-------+
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| id | name | id | score |
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+------+-------+------+-------+
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| 1 | tom | 1 | 88 |
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| 2 | berry | 2 | 99 |
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+------+-------+------+-------+
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```
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#### 1.2.5 自然连接【natural】
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```
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自动的判断连接条件，它是过同名字段来判断的
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```
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自然连接又分为：
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1. 自然内连接 natural join
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2. 自然左外连接 natural left join
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3. 自然右外连接 natural right join
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例题：
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```sql
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# 自然内连接
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mysql> select * from stuinfo natural join stumarks;
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+--------+----------+--------+--------+---------+------------+---------+-------------+---------+
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| stuNo | stuName | stuSex | stuAge | stuSeat | stuAddress | examNo | writtenExam | labExam |
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+--------+----------+--------+--------+---------+------------+---------+-------------+---------+
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| s25303 | 李斯文 | 女 | 22 | 2 | 北京 | s271811 | 80 |
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58 |
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| s25302 | 李文才 | 男 | 31 | 3 | 上海 | s271813 | 50 |
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90 |
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| s25304 | 欧阳俊雄 | 男 | 28 | 4 | 天津 | s271815 | 65 |
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50 |
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| s25301 | 张秋丽 | 男 | 18 | 1 | 北京 | s271816 | 77 |
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82 |
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| s25318 | 争青小子 | 男 | 26 | 6 | 天津 | s271819 | 56 |
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48 |
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+--------+----------+--------+--------+---------+------------+---------+-------------+---------+
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5 rows in set (0.00 sec)
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# 自然左外连接
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mysql> select * from stuinfo natural left join stumarks;
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+--------+----------+--------+--------+---------+------------+---------+-------------+---------+
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| stuNo | stuName | stuSex | stuAge | stuSeat | stuAddress | examNo | writtenExam | labExam |
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+--------+----------+--------+--------+---------+------------+---------+-------------+---------+
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| s25301 | 张秋丽 | 男 | 18 | 1 | 北京 | s271816 | 77
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82 |
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| s25302 | 李文才 | 男 | 31 | 3 | 上海 | s271813 | 50 |
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90 |
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| s25303 | 李斯文 | 女 | 22 | 2 | 北京 | s271811 | 80 |
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58 |
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| s25304 | 欧阳俊雄 | 男 | 28 | 4 | 天津 | s271815 | 65
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50 |
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| s25305 | 诸葛丽丽 | 女 | 23 | 7 | 河南 | NULL | NULL
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NULL |
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| s25318 | 争青小子 | 男 | 26 | 6 | 天津 | s271819 | 56
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48 |
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| s25319 | 梅超风 | 女 | 23 | 5 | 河北 | NULL | NULL |
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ULL |
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+--------+----------+--------+--------+---------+------------+---------+-------------+---------+
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7 rows in set (0.00 sec)
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# 自然右外连接
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mysql> select * from stuinfo natural right join stumarks;
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+--------+---------+-------------+---------+----------+--------+--------+---------+------------+
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| stuNo | examNo | writtenExam | labExam | stuName | stuSex | stuAge | stuSeat | stuAddress |
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+--------+---------+-------------+---------+----------+--------+--------+---------+------------+
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| s25303 | s271811 | 80 | 58 | 李斯文 | 女 | 22 | 2 | 北京
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| s25302 | s271813 | 50 | 90 | 李文才 | 男 | 31 | 3 | 上海
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| s25304 | s271815 | 65 | 50 | 欧阳俊雄 | 男 | 28 | 4 | 天津
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| s25301 | s271816 | 77 | 82 | 张秋丽 | 男 | 18 | 1 | 北京
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| s25318 | s271819 | 56 | 48 | 争青小子 | 男 | 26 | 6 | 天津
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| s25320 | s271820 | 66 | 77 | NULL | NULL | NULL | NULL | NULL |
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+--------+---------+-------------+---------+----------+--------+--------+---------+------------+
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6 rows in set (0.00 sec)
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```
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自然连接结论：
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1. 表连接通过同名的字段来连接的
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2. 如果没有同名的字段返回笛卡尔积
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3. 会对结果进行整理，整理的规则如下
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a) 连接字段保留一个
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b) 连接字段放在最前面
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c) 左外连接左边在前，右外连接右表在前
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#### 1.2.6 using()
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1. 用来指定连接字段。
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2. using()也会对连接字段进行整理，整理方式和自然连接是一样的。
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```sql
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mysql> select * from stuinfo inner join stumarks using(stuno); # using指定字段
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+--------+----------+--------+--------+---------+------------+---------+-------------+---------+
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| stuNo | stuName | stuSex | stuAge | stuSeat | stuAddress | examNo | writtenExam | labExam |
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+--------+----------+--------+--------+---------+------------+---------+-------------+---------+
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| s25303 | 李斯文 | 女 | 22 | 2 | 北京 | s271811 | 80 |
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58 |
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| s25302 | 李文才 | 男 | 31 | 3 | 上海 | s271813 | 50 |
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90 |
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| s25304 | 欧阳俊雄 | 男 | 28 | 4 | 天津 | s271815 | 65 |
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50 |
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| s25301 | 张秋丽 | 男 | 18 | 1 | 北京 | s271816 | 77 |
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82 |
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| s25318 | 争青小子 | 男 | 26 | 6 | 天津 | s271819 | 56 |
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48 |
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+--------+----------+--------+--------+---------+------------+---------+-------------+---------+
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5 rows in set (0.00 sec)
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```
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## 1.3 子查询
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语法
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```sql
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语法：select 语句 where 条件 (select … from 表)
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```
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1. 外面的查询称为父查询，括号中的查询称为子查询
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2. 子查询为父查询提供查询条件
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#### 1.3.1 例题
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1、查找笔试80分的学生
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```sql
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mysql> select * from stuinfo where stuno=(select stuno from stumarks where writtenexam=80);
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+--------+---------+--------+--------+---------+------------+
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| stuNo | stuName | stuSex | stuAge | stuSeat | stuAddress |
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+--------+---------+--------+--------+---------+------------+
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| s25303 | 李斯文 | 女 | 22 | 2 | 北京 |
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+--------+---------+--------+--------+---------+------------+
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```
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2、查找笔试最高分的学生
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```sql
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# 方法一：
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mysql> select * from stuinfo where stuno=(select stuno from stumarks order by writtenexam desc limit
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1);
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+--------+---------+--------+--------+---------+------------+
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| stuNo | stuName | stuSex | stuAge | stuSeat | stuAddress |
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+--------+---------+--------+--------+---------+------------+
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| s25303 | 李斯文 | 女 | 22 | 2 | 北京 |
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+--------+---------+--------+--------+---------+------------+
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1 row in set (0.00 sec)
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# 方法二：
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mysql> select * from stuinfo where stuno=(select stuno from stumarks where writtenexam=(select max(writtenexam) from stumarks));
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+--------+---------+--------+--------+---------+------------+
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| stuNo | stuName | stuSex | stuAge | stuSeat | stuAddress |
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+--------+---------+--------+--------+---------+------------+
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| s25303 | 李斯文 | 女 | 22 | 2 | 北京 |
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+--------+---------+--------+--------+---------+------------+
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1 row in set (0.00 sec)
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```
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```
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脚下留心：上面的例题，子查询只能返回一个值。如果子查询返回多个值就不能用“=”了,需要用 in
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```
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#### 1.3.2 in|not in子查询
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用于子查询的返回结果多个值。
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1、查找笔试成绩及格的同学
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```sql
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mysql> select * from stuinfo where stuno in (select stuno from stumarks where writtenexam>=60);
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+--------+----------+--------+--------+---------+------------+
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| stuNo | stuName | stuSex | stuAge | stuSeat | stuAddress |
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+--------+----------+--------+--------+---------+------------+
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| s25301 | 张秋丽 | 男 | 18 | 1 | 北京 |
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| s25303 | 李斯文 | 女 | 22 | 2 | 北京 |
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| s25304 | 欧阳俊雄 | 男 | 28 | 4 | 天津 |
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+--------+----------+--------+--------+---------+------------+
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3 rows in set (0.00 sec)
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```
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2、查询不及格的同学
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```sql
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mysql> select * from stuinfo where stuno in (select stuno from stumarks where writtenexam<=60);
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+--------+----------+--------+--------+---------+------------+
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| stuNo | stuName | stuSex | stuAge | stuSeat | stuAddress |
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+--------+----------+--------+--------+---------+------------+
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| s25302 | 李文才 | 男 | 31 | 3 | 上海 |
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| s25318 | 争青小子 | 男 | 26 | 6 | 天津 |
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+--------+----------+--------+--------+---------+------------+
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```
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3、查询没有通过的同学（不及格，缺考）
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```sql
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mysql> select * from stuinfo where stuno not in (select stuno from stumarks where writtenexam>=60);
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+--------+----------+--------+--------+---------+------------+
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| stuNo | stuName | stuSex | stuAge | stuSeat | stuAddress |
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+--------+----------+--------+--------+---------+------------+
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| s25302 | 李文才 | 男 | 31 | 3 | 上海 |
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| s25305 | 诸葛丽丽 | 女 | 23 | 7 | 河南 |
|
||
| s25318 | 争青小子 | 男 | 26 | 6 | 天津 |
|
||
| s25319 | 梅超风 | 女 | 23 | 5 | 河北 |
|
||
+--------+----------+--------+--------+---------+------------+
|
||
4 rows in set (0.00 sec)
|
||
```
|
||
|
||
#### 1.3.3 exists和not exists
|
||
|
||
1、 如果有人笔试超过80分就显示所有的学生
|
||
|
||
```sql
|
||
mysql> select * from stuinfo where exists (select * from stumarks where writtenexam>=80);
|
||
+--------+----------+--------+--------+---------+------------+
|
||
| stuNo | stuName | stuSex | stuAge | stuSeat | stuAddress |
|
||
+--------+----------+--------+--------+---------+------------+
|
||
| s25301 | 张秋丽 | 男 | 18 | 1 | 北京 |
|
||
| s25302 | 李文才 | 男 | 31 | 3 | 上海 |
|
||
| s25303 | 李斯文 | 女 | 22 | 2 | 北京 |
|
||
| s25304 | 欧阳俊雄 | 男 | 28 | 4 | 天津 |
|
||
| s25305 | 诸葛丽丽 | 女 | 23 | 7 | 河南 |
|
||
| s25318 | 争青小子 | 男 | 26 | 6 | 天津 |
|
||
| s25319 | 梅超风 | 女 | 23 | 5 | 河北 |
|
||
+--------+----------+--------+--------+---------+------------+
|
||
```
|
||
|
||
2、 如果没有人超过80分就显示所有的学生
|
||
|
||
```sql
|
||
mysql> select * from stuinfo where not exists (select * from stumarks where writtenexam>=80);
|
||
Empty set (0.02 sec)
|
||
```
|
||
|
||
#### 1.3.4 子查询分类
|
||
|
||
1、标量子查询：子查询返回的结果就一个
|
||
|
||
2、列子查询：子查询返回的结果是一个列表
|
||
|
||
3、行子查询：子查询返回的结果是一行
|
||
|
||
例题：查询成绩最高的男生和女生
|
||
|
||
```sql
|
||
mysql> select stuname,stusex,ch from stu where (stusex,ch) in (select stusex,max(ch) from stu group by stusex);
|
||
+----------+--------+------+
|
||
| stuname | stusex | ch |
|
||
+----------+--------+------+
|
||
| 争青小子 | 男 | 86 |
|
||
| Tabm | 女 | 88 |
|
||
+----------+--------+------+
|
||
```
|
||
|
||
4、表子查询：子查询返回的结果当成一个表
|
||
|
||
例题：查询成绩最高的男生和女生
|
||
|
||
```sql
|
||
mysql> select stuname,stusex,ch from (select * from stu order by ch desc) as t group by stusex;
|
||
+----------+--------+------+
|
||
| stuname | stusex | ch |
|
||
+----------+--------+------+
|
||
| Tabm | 女 | 88 |
|
||
| 争青小子 | 男 | 86 |
|
||
+----------+--------+------+
|
||
```
|
||
|
||
```
|
||
脚下留心：from后面是一个表，如果子查询的结果当成表来看，必须将子查询的结果取别名。
|
||
```
|
||
|
||
## 1.4 视图【view】
|
||
|
||
1、 视图是一张虚拟表，它表示一张表的部分或多张表的综合的结构。
|
||
|
||
2、 视图仅仅是表结构，没有表数据。视图的结构和数据建立在表的基础上。
|
||
|
||
#### 1.4.1 创建视图
|
||
|
||
语法
|
||
|
||
```sql
|
||
create [or replace] view 视图的名称
|
||
as
|
||
select语句
|
||
```
|
||
|
||
例题：
|
||
|
||
```sql
|
||
mysql> create view vw_stu
|
||
-> as
|
||
-> select stuname,stusex,writtenexam,labexam from stuinfo inner join stumarks using(stuno);
|
||
Query OK, 0 rows affected (0.00 sec)
|
||
```
|
||
|
||
```
|
||
多学一招：因为视图是一个表结构，所以创建视图后，会在数据库文件夹中多一个与视图名同名的.frm文件
|
||
```
|
||
|
||
#### 1.4.2 使用视图
|
||
|
||
视图是一张虚拟表，视图的用法和表的用法一样
|
||
|
||
```sql
|
||
mysql> select * from vw_stu;
|
||
+----------+--------+-------------+---------+
|
||
| stuname | stusex | writtenexam | labexam |
|
||
+----------+--------+-------------+---------+
|
||
| 李斯文 | 女 | 80 | 58 |
|
||
| 李文才 | 男 | 50 | 90 |
|
||
| 欧阳俊雄 | 男 | 65 | 50 |
|
||
| 张秋丽 | 男 | 77 | 82 |
|
||
| 争青小子 | 男 | 56 | 48 |
|
||
+----------+--------+-------------+---------+
|
||
|
||
mysql> update vw_stu set writtenexam=88 where stuname='李斯文';
|
||
Query OK, 1 row affected (0.05 sec)
|
||
Rows matched: 1 Changed: 1 Warnings: 0
|
||
```
|
||
|
||
#### 1.4.3 查看视图的结构
|
||
|
||
语法：
|
||
|
||
```sql
|
||
desc 视图名
|
||
```
|
||
|
||
例题
|
||
|
||
```sql
|
||
mysql> desc vw_stu;
|
||
+-------------+-------------+------+-----+---------+-------+
|
||
| Field | Type | Null | Key | Default | Extra |
|
||
+-------------+-------------+------+-----+---------+-------+
|
||
| stuname | varchar(10) | NO | | NULL | |
|
||
| stusex | char(2) | NO | | NULL | |
|
||
| writtenexam | int(11) | YES | | NULL | |
|
||
| labexam | int(11) | YES | | NULL | |
|
||
+-------------+-------------+------+-----+---------+-------+
|
||
```
|
||
|
||
#### 1.4.4 查看创建视图的语法
|
||
|
||
语法：
|
||
|
||
```sql
|
||
show create view 视图名
|
||
```
|
||
|
||
例题
|
||
|
||
|
||
|
||
#### 1.4.5 显示所有视图
|
||
|
||
```sql
|
||
#方法一：
|
||
mysql> show tables;
|
||
+------------------+
|
||
| Tables_in_itcast |
|
||
+------------------+
|
||
| stu |
|
||
| stuinfo |
|
||
| stumarks |
|
||
| t1 |
|
||
| t2 |
|
||
| vw_stu |
|
||
|
||
# 方法二
|
||
mysql> select table_name from information_schema.views;
|
||
+------------+
|
||
| table_name |
|
||
+------------+
|
||
| vw_stu |
|
||
+------------+
|
||
1 row in set (0.05 sec)
|
||
+------------------+
|
||
|
||
#方法三
|
||
mysql> show table status where comment='view' \G
|
||
*************************** 1. row ***************************
|
||
Name: vw_stu
|
||
Engine: NULL
|
||
Version: NULL
|
||
Row_format: NULL
|
||
Rows: NULL
|
||
Avg_row_length: NULL
|
||
Data_length: NULL
|
||
Max_data_length: NULL
|
||
Index_length: NULL
|
||
Data_free: NULL
|
||
Auto_increment: NULL
|
||
Create_time: NULL
|
||
Update_time: NULL
|
||
Check_time: NULL
|
||
Collation: NULL
|
||
Checksum: NULL
|
||
Create_options: NULL
|
||
Comment: VIEW
|
||
1 row in set (0.00 sec)
|
||
|
||
```
|
||
|
||
#### 1.4.6 更改视图
|
||
|
||
语法：
|
||
|
||
```sql
|
||
alter view 视图名
|
||
as
|
||
select 语句
|
||
```
|
||
|
||
例题：
|
||
|
||
```sql
|
||
mysql> alter view vw_stu
|
||
-> as
|
||
-> select * from stuinfo;
|
||
Query OK, 0 rows affected (0.00 sec)
|
||
```
|
||
|
||
#### 1.4.7 删除视图
|
||
|
||
语法：
|
||
|
||
```sql
|
||
drop view [if exists] 视图1,视图2,…
|
||
```
|
||
|
||
例题
|
||
|
||
```sql
|
||
mysql> drop view vw_stu;
|
||
Query OK, 0 rows affected (0.00 sec)
|
||
```
|
||
|
||
#### 1.4.8 视图的作用
|
||
|
||
1. 筛选数据，防止未经许可访问敏感数据
|
||
2. 隐藏表结构
|
||
3. 降低SQL语句的复杂度
|
||
|
||
#### 1.4.9 视图的算法
|
||
|
||
场景：找出语文成绩最高的男生和女生
|
||
|
||
```sql
|
||
mysql> select * from (select * from stu order by ch desc) as t group by stusex;
|
||
+--------+----------+--------+--------+---------+------------+------+------+
|
||
| stuNo | stuName | stuSex | stuAge | stuSeat | stuAddress | ch | math |
|
||
+--------+----------+--------+--------+---------+------------+------+------+
|
||
| s25321 | Tabm | 女 | 23 | 9 | 河北 | 88 | 77 |
|
||
| s25318 | 争青小子 | 男 | 26 | 6 | 天津 | 86 | 92 |
|
||
+--------+----------+--------+--------+---------+------------+------+------+
|
||
```
|
||
|
||
我们可以将子查询封装到视图中
|
||
|
||
```sql
|
||
mysql> create view vw_stu
|
||
-> as
|
||
-> select * from stu order by ch desc;
|
||
Query OK, 0 rows affected (0.00 sec)
|
||
```
|
||
|
||
可以将上面的子查询更改成视图，但是，结果和上面不一样
|
||
|
||
```sql
|
||
mysql> select * from vw_stu group by stusex;
|
||
+--------+---------+--------+--------+---------+------------+------+------+
|
||
| stuNo | stuName | stuSex | stuAge | stuSeat | stuAddress | ch | math |
|
||
+--------+---------+--------+--------+---------+------------+------+------+
|
||
| s25301 | 张秋丽 | 男 | 18 | 1 | 北京 | 80 | NULL |
|
||
| s25303 | 李斯文 | 女 | 22 | 2 | 北京 | 55 | 82 |
|
||
+--------+---------+--------+--------+---------+------------+------+------+
|
||
```
|
||
|
||
原因：这是因为视图的算法造成的
|
||
|
||
```
|
||
1. merge：合并算法，将视图的语句和外层的语句合并后在执行。
|
||
2. temptable：临时表算法，将视图生成一个临时表，再执行外层语句
|
||
3. undefined：未定义，MySQL到底用merge还是用temptable由MySQL决定，这是一个默认的算法，一般视图都会选择merge算法，因为merge效率高。
|
||
```
|
||
|
||
解决：在创建视图的时候指定视图的算法
|
||
|
||
```sql
|
||
create algorithm=temptable view 视图名
|
||
as
|
||
select 语句
|
||
```
|
||
|
||
指定算法创建视图
|
||
|
||
```sql
|
||
mysql> create algorithm=temptable view vw_stu
|
||
-> as
|
||
-> select * from stu order by ch desc;
|
||
Query OK, 0 rows affected (0.00 sec)
|
||
|
||
mysql> select * from vw_stu group by stusex; # 结果是一致的
|
||
+--------+----------+--------+--------+---------+------------+------+------+
|
||
| stuNo | stuName | stuSex | stuAge | stuSeat | stuAddress | ch | math |
|
||
+--------+----------+--------+--------+---------+------------+------+------+
|
||
| s25321 | Tabm | 女 | 23 | 9 | 河北 | 88 | 77 |
|
||
| s25318 | 争青小子 | 男 | 26 | 6 | 天津 | 86 | 92 |
|
||
+--------+----------+--------+--------+---------+------------+------+------+
|
||
```
|
||
|
||
## 1.5 事务【transaction】
|
||
|
||
1. 事务是一个不可分割的执行单元
|
||
2. 事务作为一个整体要么一起执行，要么一起回滚
|
||
|
||
插入测试数据
|
||
|
||
```sql
|
||
mysql> create table bank(
|
||
-> cardid char(4) primary key,
|
||
-> money int
|
||
-> );
|
||
Query OK, 0 rows affected (0.00 sec)
|
||
|
||
mysql> insert into bank values ('1001',1000),('1002',100);
|
||
Query OK, 2 rows affected (0.00 sec)
|
||
Records: 2 Duplicates: 0 Warnings: 0
|
||
```
|
||
|
||
#### 1.5.1 事务操作
|
||
|
||
```sql
|
||
开启事务：start transaction或begin [work]
|
||
提交事务：commit
|
||
回滚事务：rollback
|
||
```
|
||
|
||
例题：
|
||
|
||
```sql
|
||
mysql> delimiter // # 更改定界符
|
||
|
||
mysql> start transaction; # 开启事务
|
||
-> update bank set money=money-100 where cardid='1001';
|
||
-> update bank set money=money+100 where cardid='1002' //
|
||
Query OK, 0 rows affected (0.00 sec)
|
||
|
||
mysql> commit // # 提交事务
|
||
|
||
mysql> rollback // # 回滚事务
|
||
```
|
||
|
||
```
|
||
思考：事务什么时候产生？什么时候结束？
|
||
答：开启的时候产生，提交事务或回滚事务都结束
|
||
|
||
脚下留心：只有innodb和BDB才支持事务，myisam不支持事务。
|
||
```
|
||
|
||
#### 1.5.2 设置事务的回滚点
|
||
|
||
语法：
|
||
|
||
```sql
|
||
设置回滚点： savepoint 回滚点名
|
||
回滚到回滚点： rollback to 回滚点
|
||
```
|
||
|
||
例题：
|
||
|
||
```sql
|
||
mysql> start transaction;
|
||
Query OK, 0 rows affected (0.00 sec)
|
||
|
||
mysql> insert into bank values ('1003',1000);
|
||
Query OK, 1 row affected (0.00 sec)
|
||
|
||
mysql> savepoint aa; # 设置回滚点 aa
|
||
Query OK, 0 rows affected (0.00 sec)
|
||
|
||
mysql> insert into bank values ('1004',500);
|
||
Query OK, 1 row affected (0.00 sec)
|
||
|
||
mysql> savepoint bb; # 设置回滚点bb
|
||
Query OK, 0 rows affected (0.00 sec)
|
||
|
||
mysql> rollback to aa; # 回滚到aa点
|
||
Query OK, 0 rows affected (0.00 sec)
|
||
|
||
mysql> commit; # 提交事务
|
||
|
||
mysql> select * from bank ;
|
||
+--------+-------+
|
||
| cardid | money |
|
||
+--------+-------+
|
||
| 1001 | 800 |
|
||
| 1002 | 200 |
|
||
| 1003 | 1000 |
|
||
+--------+-------+
|
||
```
|
||
|
||
#### 1.5.3 事务的特性（ACID）
|
||
|
||
1. 原子性（Atomicity）：事务是一个整体，不可以再分，要么一起执行，要么一起不执行。
|
||
2. 一致性（Consistency）：事务完成时，数据必须处于一致的状态。
|
||
3. 隔离性（Isolation）：每个事务都是相互隔离的
|
||
4. 永久性（Durability）：事务完成后，对数据的修改是永久性的。
|
||
|
||
## 1.6 索引【index】
|
||
|
||
索引的优点：查询速度快
|
||
|
||
索引的缺点：
|
||
|
||
1. 增、删、改（数据操作语句）效率低了
|
||
2. 索引占用空间
|
||
|
||
#### 1.6.1 索引的类型
|
||
|
||
1. 普通索引
|
||
|
||
2. 唯一索引（唯一键）
|
||
3. 主键索引：只要主键就自动创建主键索引，不需要手动创建。
|
||
4. 全文索引，搜索引擎使用，MySQL不支持中文的全文索引，我们通过sphinx去解决中文的全文索引。
|
||
|
||
#### 1.6.2 创建普通索引【create index】
|
||
|
||
语法：
|
||
|
||
```sql
|
||
create index [索引名] on 表名 （字段名）
|
||
alter table 表名 add index [索引的名称] （列名）
|
||
```
|
||
|
||
例题：
|
||
|
||
```sql
|
||
# 创建索引方法一
|
||
mysql> create index ix_stuname on stuinfo(stuname);
|
||
Query OK, 0 rows affected (0.08 sec)
|
||
Records: 0 Duplicates: 0 Warnings: 0
|
||
|
||
# 创建索引方法二
|
||
mysql> alter table stuinfo add index ix_address (stuaddress);
|
||
Query OK, 0 rows affected (0.08 sec)
|
||
Records: 0 Duplicates: 0 Warnings: 0
|
||
|
||
# 创建表的时候就添加索引
|
||
mysql> create table emp(
|
||
-> id int,
|
||
-> name varchar(10),
|
||
-> index ix_name (name) # 创建索引
|
||
-> );
|
||
Query OK, 0 rows affected (0.00 sec)
|
||
```
|
||
|
||
#### 1.6.3 创建唯一索引
|
||
|
||
```sql
|
||
语法一：create unique index 索引名 on 表名 （字段名）
|
||
语法二：alter table 表名 add unqiue [index] [索引的名称] （列名）
|
||
语法三：创建表的时候添加唯一索引，和创建唯一键是一样的。
|
||
```
|
||
|
||
例题
|
||
|
||
```sql
|
||
# 方法一：
|
||
mysql> create unique index UQ_stuname on stu(stuname);
|
||
Query OK, 0 rows affected (0.06 sec)
|
||
Records: 0 Duplicates: 0 Warnings: 0
|
||
|
||
# 方法二：
|
||
mysql> alter table stu add unique UQ_address (stuaddress);
|
||
Query OK, 0 rows affected (0.02 sec)
|
||
Records: 0 Duplicates: 0 Warnings: 0
|
||
|
||
# 方法三
|
||
mysql> create table stu2(
|
||
-> id int,
|
||
-> name varchar(20),
|
||
-> unique UQ_name(name)
|
||
-> );
|
||
Query OK, 0 rows affected (0.01 sec)
|
||
```
|
||
|
||
#### 1.6.4 删除索引
|
||
|
||
语法
|
||
|
||
```sql
|
||
drop index 索引名 on 表名
|
||
```
|
||
|
||
例题
|
||
|
||
```sql
|
||
mysql> drop index ix_stuname on stuinfo;
|
||
Query OK, 0 rows affected (0.03 sec)
|
||
Records: 0 Duplicates: 0 Warnings: 0
|
||
```
|
||
|
||
#### 1.6.5 创建索引的指导原则
|
||
|
||
1. 该列用于频繁搜索
|
||
|
||
2. 改列用于排序
|
||
3. 公共字段要创建索引
|
||
4. 如果表中的数据很少，不需要创建索引。MySQL搜索索引的时间比逐条搜索数据的时间要长。
|
||
5. 如果一个字段上的数据只有几个不同的值，改字段不适合做索引，比如性别。
|
||
|
||
## 1.7 函数
|
||
|
||
#### 1.7.1 数字类
|
||
|
||
```sql
|
||
mysql> select rand(); # 生成随机数
|
||
+---------------------+
|
||
| rand() |
|
||
+---------------------+
|
||
| 0.18474003969201822 |
|
||
+---------------------+
|
||
1 row in set (0.00 sec)
|
||
|
||
mysql> select * from stuinfo order by rand(); # 随机排序
|
||
|
||
mysql> select * from stuinfo order by rand() limit 2; # 随机抽两个学生
|
||
+--------+----------+--------+--------+---------+------------+
|
||
| stuNo | stuName | stuSex | stuAge | stuSeat | stuAddress |
|
||
+--------+----------+--------+--------+---------+------------+
|
||
| s25305 | 诸葛丽丽 | 女 | 23 | 7 | 河南 |
|
||
| s25304 | 欧阳俊雄 | 男 | 28 | 4 | 天津 |
|
||
+--------+----------+--------+--------+---------+------------+
|
||
2 rows in set (0.00 sec)
|
||
|
||
mysql> select round(3.5); #四舍五入
|
||
+------------+
|
||
| round(3.5) |
|
||
+------------+
|
||
| 4 |
|
||
+------------+
|
||
1 row in set (0.00 sec)
|
||
|
||
mysql> select ceil(3.1); # 向上取整
|
||
+-----------+
|
||
| ceil(3.1) |
|
||
+-----------+
|
||
| 4 |
|
||
+-----------+
|
||
1 row in set (0.00 sec)
|
||
|
||
mysql> select floor(3.9); # 向下取整
|
||
+------------+
|
||
| floor(3.9) |
|
||
+------------+
|
||
| 3 |
|
||
+------------+
|
||
1 row in set (0.00 sec)
|
||
|
||
mysql> select truncate(3.1415926,3); # 截取数字
|
||
+-----------------------+
|
||
| truncate(3.1415926,3) |
|
||
+-----------------------+
|
||
| 3.141 |
|
||
+-----------------------+
|
||
1 row in set (0.00 sec)
|
||
```
|
||
|
||
#### 1.7.2 字符串类
|
||
|
||
```sql
|
||
mysql> select ucase('i am a boy!'); # 转成大写
|
||
+----------------------+
|
||
| ucase('i am a boy!') |
|
||
+----------------------+
|
||
| I AM A BOY! |
|
||
+----------------------+
|
||
1 row in set (0.00 sec)
|
||
|
||
mysql> select lcase('I Am A Boy!'); #转成小写
|
||
+----------------------+
|
||
| lcase('I Am A Boy!') |
|
||
+----------------------+
|
||
| i am a boy! |
|
||
+----------------------+
|
||
1 row in set (0.00 sec)
|
||
|
||
mysql> select left('abcde',3); # 从左边开始截取，截取3个
|
||
+-----------------+
|
||
| left('abcde',3) |
|
||
+-----------------+
|
||
| abc |
|
||
+-----------------+
|
||
1 row in set (0.00 sec)
|
||
|
||
mysql> select right('abcde',3); # 从右边开始截取，截取3个
|
||
+------------------+
|
||
| right('abcde',3) |
|
||
+------------------+
|
||
| cde |
|
||
+------------------+
|
||
1 row in set (0.00 sec)
|
||
|
||
mysql> select substring('abcde',2,3); #从第2个位置开始截取，截取3个【位置从1开始】
|
||
+------------------------+
|
||
| substring('abcde',2,3) |
|
||
+------------------------+
|
||
| bcd |
|
||
+------------------------+
|
||
1 row in set (0.00 sec)
|
||
|
||
mysql> select concat('中国','上海'); # 字符串相连
|
||
+-----------------------+
|
||
| concat('中国','上海') |
|
||
+-----------------------+
|
||
| 中国上海 |
|
||
+-----------------------+
|
||
1 row in set (0.00 sec)
|
||
|
||
mysql> select concat(stuname,'-',stusex) from stuinfo; # 将表中的姓名和性别连接起来
|
||
+----------------------------+
|
||
| concat(stuname,'-',stusex) |
|
||
+----------------------------+
|
||
| 张秋丽-男 |
|
||
| 李文才-男 |
|
||
| 李斯文-女 |
|
||
| 欧阳俊雄-男 |
|
||
| 诸葛丽丽-女 |
|
||
| 争青小子-男 |
|
||
| 梅超风-女 |
|
||
+----------------------------+
|
||
7 rows in set (0.00 sec)
|
||
|
||
# coalesce(字段1，字段2) 如果字段1不为空就显示字段1，否则，显示字段2
|
||
mysql> select stuname,coalesce(writtenexam,'缺考'),coalesce(labexam,'缺考') from stuinfo natural left join stumarks; # 将考试成绩为空的显示为缺考
|
||
+----------+------------------------------+--------------------------+
|
||
| stuname | coalesce(writtenexam,'缺考') | coalesce(labexam,'缺考') |
|
||
+----------+------------------------------+--------------------------+
|
||
| 张秋丽 | 77 | 82 |
|
||
| 李文才 | 50 | 90 |
|
||
| 李斯文 | 88 | 58 |
|
||
| 欧阳俊雄 | 65 | 50 |
|
||
| 诸葛丽丽 | 缺考 | 缺考 |
|
||
| 争青小子 | 56 | 48 |
|
||
| 梅超风 | 缺考 | 缺考 |
|
||
+----------+------------------------------+--------------------------+
|
||
|
||
mysql> select length('锄禾日当午'); # 字节长度
|
||
+----------------------+
|
||
| length('锄禾日当午') |
|
||
+----------------------+
|
||
| 10 |
|
||
+----------------------+
|
||
1 row in set (0.00 sec)
|
||
|
||
mysql> select char_length('锄禾日当午'); # 字符个数
|
||
+---------------------------+
|
||
| char_length('锄禾日当午') |
|
||
+---------------------------+
|
||
| 5 |
|
||
+---------------------------+
|
||
1 row in set (0.00 sec)
|
||
```
|
||
|
||
#### 1.7.3 时间类
|
||
|
||
```sql
|
||
mysql> select unix_timestamp(); #获取时间戳
|
||
+------------------+
|
||
| unix_timestamp() |
|
||
+------------------+
|
||
| 1537084508 |
|
||
+------------------+
|
||
1 row in set (0.00 sec)
|
||
|
||
mysql> select from_unixtime(unix_timestamp()); # 将时间戳转成年-月-日 小时:分钟:秒的格式
|
||
+---------------------------------+
|
||
| from_unixtime(unix_timestamp()) |
|
||
+---------------------------------+
|
||
| 2018-09-16 15:55:56 |
|
||
+---------------------------------+
|
||
1 row in set (0.00 sec)
|
||
|
||
mysql> select now(); # 获取当前日期时间
|
||
+---------------------+
|
||
| now() |
|
||
+---------------------+
|
||
| 2018-09-16 15:57:04 |
|
||
+---------------------+
|
||
1 row in set (0.00 sec)
|
||
|
||
mysql> select year(now()) 年,month(now()) 月, day(now()) 日,hour(now()) 小,minute(now()) 分钟,second(now()) 秒;
|
||
+------+------+------+------+------+------+
|
||
| 年 | 月 | 日 | 小时 | 分钟 | 秒 |
|
||
+------+------+------+------+------+------+
|
||
| 2018 | 9 | 16 | 15 | 59 | 14 |
|
||
+------+------+------+------+------+------+
|
||
1 row in set (0.00 sec)
|
||
|
||
mysql> select dayname(now()) 星期,monthname(now()),dayofyear(now()) 本年的第几天;
|
||
+--------+------------------+--------------+
|
||
| 星期 | monthname(now()) | 本年的第几天 |
|
||
+--------+------------------+--------------+
|
||
| Sunday | September | 259 |
|
||
+--------+------------------+--------------+
|
||
1 row in set (0.00 sec)
|
||
|
||
mysql> select datediff(now(),'2008-8-8'); # 日期相减
|
||
+----------------------------+
|
||
| datediff(now(),'2008-8-8') |
|
||
+----------------------------+
|
||
| 3691 |
|
||
+----------------------------+
|
||
1 row in set (0.00 sec)
|
||
|
||
mysql> select convert(now(),date),convert(now(),time); # 将now()转成日期和时间
|
||
+---------------------+---------------------+
|
||
| convert(now(),date) | convert(now(),time) |
|
||
+---------------------+---------------------+
|
||
| 2018-09-16 | 16:07:24 |
|
||
+---------------------+---------------------+
|
||
|
||
mysql> select cast(now() as date),cast(now() as time); # 将now()转成日期和时间
|
||
+---------------------+---------------------+
|
||
| cast(now() as date) | cast(now() as time) |
|
||
+---------------------+---------------------+
|
||
| 2018-09-16 | 16:08:03 |
|
||
+---------------------+---------------------+
|
||
1 row in set (0.00 sec)
|
||
```
|
||
|
||
#### 1.7.4 加密函数
|
||
|
||
```sql
|
||
+----------------------------------+------------------------------------------+
|
||
| md5('root') | sha('root') |
|
||
+----------------------------------+------------------------------------------+
|
||
| 63a9f0ea7bb98050796b649e85481845 | dc76e9f0c0006e8f919e0c515c66dbba3982f785 |
|
||
+----------------------------------+------------------------------------------+
|
||
1 row in set (0.00 sec)
|
||
```
|
||
|
||
#### 1.7.5 判断函数
|
||
|
||
语法
|
||
|
||
```sql
|
||
if(表达式,值1,值2)
|
||
```
|
||
|
||
例题：
|
||
|
||
```sql
|
||
mysql> select if(10%2=0,'偶数','奇数');
|
||
+--------------------------+
|
||
| if(10%2=0,'偶数','奇数') |
|
||
+--------------------------+
|
||
| 偶数 |
|
||
+--------------------------+
|
||
1 row in set (0.00 sec)
|
||
|
||
# 语文和数学都超过60分才通过
|
||
mysql> select stuname,ch,math,if(ch>=60 && math>=60,'通过','不通过') '是否通过' from stu;
|
||
+----------+------+------+----------+
|
||
| stuname | ch | math | 是否通过 |
|
||
+----------+------+------+----------+
|
||
| 张秋丽 | 80 | NULL | 不通过 |
|
||
| 李文才 | 77 | 76 | 通过 |
|
||
| 李斯文 | 55 | 82 | 不通过 |
|
||
| 欧阳俊雄 | NULL | 74 | 不通过 |
|
||
| 诸葛丽丽 | 72 | 56 | 不通过 |
|
||
| 争青小子 | 86 | 92 | 通过 |
|
||
| 梅超风 | 74 | 67 | 通过 |
|
||
| Tom | 65 | 67 | 通过 |
|
||
| Tabm | 88 | 77 | 通过 |
|
||
+----------+------+------+----------+
|
||
9 rows in set (0.00 sec)
|
||
```
|
||
|
||
## 1.8 预处理
|
||
|
||
预编译一次，可以多次执行。用来解决一条SQL语句频繁执行的问题。
|
||
|
||
```
|
||
预处理语句：prepare 预处理名字 from ‘sql语句’
|
||
执行预处理：execute 预处理名字 [using 变量]
|
||
```
|
||
|
||
例题一：
|
||
|
||
```sql
|
||
mysql> prepare stmt from 'select * from stuinfo'; # 创建预处理
|
||
Query OK, 0 rows affected (0.00 sec)
|
||
Statement prepared
|
||
|
||
mysql> execute stmt; # 执行预处理
|
||
+--------+----------+--------+--------+---------+------------+
|
||
| stuNo | stuName | stuSex | stuAge | stuSeat | stuAddress |
|
||
+--------+----------+--------+--------+---------+------------+
|
||
| s25301 | 张秋丽 | 男 | 18 | 1 | 北京 |
|
||
| s25302 | 李文才 | 男 | 31 | 3 | 上海 |
|
||
| s25303 | 李斯文 | 女 | 22 | 2 | 北京 |
|
||
| s25304 | 欧阳俊雄 | 男 | 28 | 4 | 天津 |
|
||
| s25305 | 诸葛丽丽 | 女 | 23 | 7 | 河南 |
|
||
| s25318 | 争青小子 | 男 | 26 | 6 | 天津 |
|
||
| s25319 | 梅超风 | 女 | 23 | 5 | 河北 |
|
||
+--------+----------+--------+--------+---------+------------+
|
||
7 rows in set (0.00 sec)
|
||
```
|
||
|
||
例题二：传递参数
|
||
|
||
```sql
|
||
mysql> delimiter //
|
||
mysql> prepare stmt from 'select * from stuinfo where stuno=?' // -- ?是位置占位符
|
||
Query OK, 0 rows affected (0.00 sec)
|
||
Statement prepared
|
||
|
||
mysql> set @id='s25301'; -- 变量以@开头，通过set给变量赋值
|
||
-> execute stmt using @id // -- 执行预处理，传递参数
|
||
Query OK, 0 rows affected (0.00 sec)
|
||
|
||
+--------+---------+--------+--------+---------+------------+
|
||
| stuNo | stuName | stuSex | stuAge | stuSeat | stuAddress |
|
||
+--------+---------+--------+--------+---------+------------+
|
||
| s25301 | 张秋丽 | 男 | 18 | 1 | 北京 |
|
||
+--------+---------+--------+--------+---------+------------+
|
||
1 row in set (0.00 sec)
|
||
```
|
||
|
||
```
|
||
脚下留心：
|
||
1、?是位置占位符
|
||
2、变量以@开头
|
||
3、通过set给变量赋值
|
||
```
|
||
|
||
例题三：传递多个参数
|
||
|
||
```sql
|
||
mysql> prepare stmt from 'select * from stuinfo where stusex=? and stuaddress=?' //
|
||
Query OK, 0 rows affected (0.00 sec)
|
||
Statement prepared
|
||
|
||
mysql> set @sex='男';
|
||
-> set @addr='北京';
|
||
-> execute stmt using @sex,@addr //
|
||
Query OK, 0 rows affected (0.00 sec)
|
||
|
||
Query OK, 0 rows affected (0.00 sec)
|
||
|
||
+--------+---------+--------+--------+---------+------------+
|
||
| stuNo | stuName | stuSex | stuAge | stuSeat | stuAddress |
|
||
+--------+---------+--------+--------+---------+------------+
|
||
| s25301 | 张秋丽 | 男 | 18 | 1 | 北京 |
|
||
+--------+---------+--------+--------+---------+------------+
|
||
1 row in set (0.00 sec)
|
||
```
|
||
|
||
## 1.9 存储过程【procedure】
|
||
|
||
#### 1.7.1 存储过程的优点
|
||
|
||
1. 存储过程可以减少网络流量
|
||
2. 允许模块化设计
|
||
3. 支持事务
|
||
|
||
#### 1.7.2 创建存储过程
|
||
|
||
语法：
|
||
|
||
```sql
|
||
create procedure 存储过程名(参数)
|
||
begin
|
||
//sql语句
|
||
end;
|
||
|
||
脚下留心：由于过程中有很多SQL语句，每个语句的结束都要用（；）结束。默认情况下，分号既表示语句结束，又表示向服务器发送SQL语句。我们希望分号仅表示语句的结束，不要将SQL语句发送到服务器执行，通过delimiter来更改结束符。
|
||
```
|
||
|
||
例题
|
||
|
||
```sql
|
||
mysql> delimiter //
|
||
mysql> create procedure proc() -- 创建存储过程
|
||
-> begin
|
||
-> select * from stuinfo;
|
||
-> end //
|
||
Query OK, 0 rows affected (0.00 sec)
|
||
```
|
||
|
||
#### 1.7.3 调用存储过程
|
||
|
||
语法：
|
||
|
||
```sql
|
||
call 存储过程名()
|
||
```
|
||
|
||
例题：
|
||
|
||
```sql
|
||
mysql> call proc() // -- 调用存储过程
|
||
+--------+----------+--------+--------+---------+------------+
|
||
| stuNo | stuName | stuSex | stuAge | stuSeat | stuAddress |
|
||
+--------+----------+--------+--------+---------+------------+
|
||
| s25301 | 张秋丽 | 男 | 18 | 1 | 北京 |
|
||
| s25302 | 李文才 | 男 | 31 | 3 | 上海 |
|
||
| s25303 | 李斯文 | 女 | 22 | 2 | 北京 |
|
||
| s25304 | 欧阳俊雄 | 男 | 28 | 4 | 天津 |
|
||
| s25305 | 诸葛丽丽 | 女 | 23 | 7 | 河南 |
|
||
| s25318 | 争青小子 | 男 | 26 | 6 | 天津 |
|
||
| s25319 | 梅超风 | 女 | 23 | 5 | 河北 |
|
||
+--------+----------+--------+--------+---------+------------+
|
||
7 rows in set (0.00 sec)
|
||
```
|
||
|
||
#### 1.7.4 删除存储过程
|
||
|
||
语法
|
||
|
||
```sql
|
||
drop procedure [if exists] 存储过程名
|
||
```
|
||
|
||
例题：
|
||
|
||
```sql
|
||
mysql> drop procedure proc // -- 删除存储过程
|
||
Query OK, 0 rows affected (0.00 sec)
|
||
```
|
||
|
||
#### 1.7.5 查看存储过程的信息
|
||
|
||
```sql
|
||
show create procedure 存储过程名\G
|
||
```
|
||
|
||
例题
|
||
|
||
```sql
|
||
mysql> show create procedure proc \G
|
||
*************************** 1. row ***************************
|
||
Procedure: proc
|
||
sql_mode: STRICT_TRANS_TABLES,NO_AUTO_CREATE_USER,NO_ENGINE_SUBSTITUTION
|
||
Create Procedure: CREATE DEFINER=`root`@`localhost` PROCEDURE `proc`()
|
||
begin
|
||
select * from stuinfo;
|
||
end
|
||
character_set_client: gbk
|
||
collation_connection: gbk_chinese_ci
|
||
Database Collation: utf8_general_ci
|
||
1 row in set (0.00 sec)
|
||
```
|
||
|
||
#### 1.7.6 显示所有的存储过程
|
||
|
||
```sql
|
||
mysql> show procedure status \G
|
||
```
|
||
|
||
#### 1.7.7 存储过程的参数
|
||
|
||
存储过程的参数分为：输入参数（in）【默认】，输出参数（out），输入输出参数（inout）
|
||
|
||
存储过程不能使用return返回值，要返回值只能通过“输出参数”来向外传递值。
|
||
|
||
例题一：传递学号，获取对应的信息
|
||
|
||
```sql
|
||
mysql> create procedure proc(in param varchar(10)) -- 输入参数
|
||
-> select * from stuinfo where stuno=param //
|
||
Query OK, 0 rows affected (0.00 sec)
|
||
|
||
mysql> call proc('s25301') //
|
||
+--------+---------+--------+--------+---------+------------+
|
||
| stuNo | stuName | stuSex | stuAge | stuSeat | stuAddress |
|
||
+--------+---------+--------+--------+---------+------------+
|
||
| s25301 | 张秋丽 | 男 | 18 | 1 | 北京 |
|
||
+--------+---------+--------+--------+---------+------------+
|
||
1 row in set (0.00 sec)
|
||
```
|
||
|
||
例题二：查找同桌
|
||
|
||
```sql
|
||
mysql> create procedure proc(name varchar(10))
|
||
-> begin
|
||
-> declare seat tinyint; -- 声明局部变量
|
||
-> select stuseat into seat from stuinfo where stuname=name; -- 将座位号保存到变量中
|
||
-> select * from stuinfo where stuseat=seat+1 or stuseat=seat-1; -- 查找同桌
|
||
-> end //
|
||
Query OK, 0 rows affected (0.00 sec)
|
||
|
||
mysql> call proc('李文才') //
|
||
+--------+----------+--------+--------+---------+------------+
|
||
| stuNo | stuName | stuSex | stuAge | stuSeat | stuAddress |
|
||
+--------+----------+--------+--------+---------+------------+
|
||
| s25303 | 李斯文 | 女 | 22 | 2 | 北京 |
|
||
| s25304 | 欧阳俊雄 | 男 | 28 | 4 | 天津 |
|
||
+--------+----------+--------+--------+---------+------------+
|
||
2 rows in set (0.00 sec)
|
||
```
|
||
|
||
强调
|
||
|
||
```
|
||
1、通过declare关键字声明局部变量；全局变量@开头就可以了
|
||
2、给变量赋值有两种方法
|
||
方法一：set 变量名=值
|
||
方法二：select 字段 into 变量 from 表 where 条件
|
||
3、声明的变量不能与列名同名
|
||
```
|
||
|
||
例题三：输出参数
|
||
|
||
```sql
|
||
mysql> create procedure proc(num int, out result int) //out 表示输出参数
|
||
-> begin
|
||
-> set result=num*num;
|
||
-> end //
|
||
Query OK, 0 rows affected (0.00 sec)
|
||
|
||
mysql> call proc(10,@result) //
|
||
Query OK, 0 rows affected (0.00 sec)
|
||
|
||
mysql> select @result //
|
||
+---------+
|
||
| @result |
|
||
+---------+
|
||
| 100 |
|
||
+---------+
|
||
1 row in set (0.00 sec)
|
||
```
|
||
|
||
|
||
|
||
例题四：输入输出参数
|
||
|
||
```sql
|
||
mysql> create procedure proc(inout num int) # inout 表示是输入输出参数
|
||
-> begin
|
||
-> set num=num*num;
|
||
-> end //
|
||
Query OK, 0 rows affected (0.00 sec)
|
||
|
||
mysql> set @num=10;
|
||
-> call proc(@num);
|
||
-> select @num //
|
||
Query OK, 0 rows affected (0.00 sec)
|
||
|
||
Query OK, 0 rows affected (0.00 sec)
|
||
|
||
+------+
|
||
| @num |
|
||
+------+
|
||
| 100 |
|
||
+------+
|
||
1 row in set (0.00 sec)
|
||
```
|