87 lines
2.0 KiB
Markdown
87 lines
2.0 KiB
Markdown
### 练习一
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**1**
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```sql
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#(1)创建数据库
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CREATE DATABASE test04_Market DEFAULT CHARACTER SET utf8;
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USE test04_Market;
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#(2)创建数据表
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CREATE TABLE customers(
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c_num INT(11) PRIMARY KEY AUTO_INCREMENT,
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c_name VARCHAR(50),
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c_contact VARCHAR(50),
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c_city VARCHAR(50),
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c_birth DATETIME NOT NULL
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);
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#(3)更改字段的位置
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#AFTER/BEFORE 字段名 设置位置在指定字段前/后
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ALTER TABLE 表名 MODIFY 字段名 数据类型 AFTER/BEFORE 字段名;
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ALTER TABLE customers MODIFY c_contact VARCHAR(50) AFTER c_birth;
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#(4)更改字段的数据类型
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ALTER TABLE customers MODIFY c_name VARCHAR(70);
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#(5)更改字段名
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ALTER TABLE customers CHANGE c_contact c_phone VARCHAR(50);
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#(6)添加字段
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ALTER TABLE customers ADD c_gender CHAR(1);
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#(7)更改表名
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ALTER TABLE customers RENAME TO customers_info;
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#(8)删除字段
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ALTER TABLE customers_info DROP c_city;
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```
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**2**
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```sql
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#(1)创建表时 添加外键约束并指定外键约束名称
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CREATE TABLE orders(
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o_num INT(11) PRIMARY KEY AUTO_INCREMENT,
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o_date DATE,
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c_id INT(11),
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CONSTRAINT fk_cid FOREIGN KEY(c_id) REFERENCES customers_info(c_num)
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);
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#(2)
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#删除指定外键
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ALTER TABLE orders DROP FOREIGN KEY orders_ibfk_1;
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#删除指定表
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DROP TABLE orders;
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```
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---
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### 练习二
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```sql
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#(1)创建表、插入记录
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CREATE TABLE pet(
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`name` VARCHAR(20) NOT NULL COMMENT '宠物名称',
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`owner` VARCHAR(20) COMMENT '宠物主人',
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species VARCHAR(20) NOT NULL COMMENT '种类',
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sex CHAR(1) NOT NULL COMMENT '性别',
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birth YEAR NOT NULL COMMENT '出生日期',
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death YEAR COMMENT '死亡日期'
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);
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INSERT INTO pet()
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VALUES
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('Fluffy', 'Harold', 'cat', 'f', 2003, 2010),
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('Claws', 'Gwen', 'cat', 'm', 2004,NULL ),
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('Buffy', NULL, 'dog', 'f', 2009, NULL),
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('Fang', 'Benny', 'dog', 'm', 2000, NULL),
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('Bowser', 'Diane', 'dog', 'm', 2003, 2009),
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('Chirpy', NULL, 'bird', 'f', 2008, NULL);
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#(2)更新记录
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UPDATE pet
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SET `owner` = 'Kevin'
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WHERE `name` = 'Fang';
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#(3)
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UPDATE pet
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SET `owner` = 'Kevin'
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WHERE `owner` IS NULL;
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#(4)
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DELETE FROM pet
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WHERE death IS NOT NULL;
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#(5)
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TRUNCATE pet;
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```
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