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2208/MySQL数据库操作综合练习题答案.md

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+### 练习一
+
+**1**
+
+```sql
+#(1)创建数据库
+CREATE DATABASE test04_Market DEFAULT CHARACTER SET utf8;
+USE test04_Market;
+#(2)创建数据表
+CREATE TABLE customers(
+	c_num INT(11) PRIMARY KEY	AUTO_INCREMENT,
+	c_name VARCHAR(50),
+	c_contact VARCHAR(50),
+	c_city VARCHAR(50),
+	c_birth DATETIME NOT NULL
+);
+#(3)更改字段的位置
+#AFTER/BEFORE 字段名 设置位置在指定字段前/后
+ALTER TABLE 表名 MODIFY 字段名 数据类型 AFTER/BEFORE 字段名;
+ALTER TABLE customers MODIFY c_contact VARCHAR(50) AFTER c_birth;
+#(4)更改字段的数据类型
+ALTER TABLE customers MODIFY c_name VARCHAR(70);
+#(5)更改字段名
+ALTER TABLE customers CHANGE c_contact c_phone VARCHAR(50);
+#(6)添加字段
+ALTER TABLE customers ADD c_gender CHAR(1);
+#(7)更改表名
+ALTER TABLE customers RENAME TO customers_info;
+#(8)删除字段
+ALTER TABLE customers_info DROP c_city;
+```
+
+**2**
+
+```sql
+#(1)创建表时 添加外键约束并指定外键约束名称
+CREATE TABLE orders(
+	o_num INT(11) PRIMARY KEY AUTO_INCREMENT,
+	o_date DATE,
+	c_id INT(11),
+	CONSTRAINT fk_cid FOREIGN KEY(c_id) REFERENCES customers_info(c_num)
+);
+#(2)
+#删除指定外键
+ALTER TABLE orders DROP FOREIGN KEY orders_ibfk_1;
+#删除指定表
+DROP TABLE orders;
+```
+
+---
+
+### 练习二
+
+```sql
+#(1)创建表、插入记录
+CREATE TABLE pet(
+	`name` VARCHAR(20) NOT NULL COMMENT '宠物名称',
+	`owner` VARCHAR(20) COMMENT '宠物主人',
+	species VARCHAR(20) NOT NULL COMMENT '种类',
+	sex CHAR(1) NOT NULL COMMENT '性别',
+	birth YEAR NOT NULL COMMENT '出生日期',
+	death YEAR COMMENT '死亡日期'
+);
+INSERT INTO pet()
+VALUES
+('Fluffy', 'Harold', 'cat', 'f', 2003, 2010),
+('Claws', 'Gwen', 'cat', 'm', 2004,NULL ),
+('Buffy', NULL, 'dog', 'f', 2009, NULL),
+('Fang', 'Benny', 'dog', 'm', 2000, NULL),
+('Bowser', 'Diane', 'dog', 'm', 2003, 2009),
+('Chirpy', NULL, 'bird', 'f', 2008, NULL);
+#(2)更新记录
+UPDATE pet
+SET `owner` = 'Kevin'
+WHERE `name` = 'Fang';
+#(3)
+UPDATE pet
+SET `owner` = 'Kevin'
+WHERE `owner` IS NULL;
+#(4)
+DELETE FROM pet
+WHERE death IS NOT NULL;
+#(5)
+TRUNCATE pet;
+```
+
+### 练习三
+
+```sql
+#1.创建数据库
+CREATE DATABASE test_compay DEFAULT CHARACTER SET utf8;
+
+#2.创建表
+CREATE TABLE department(
+	depid INT PRIMARY KEY AUTO_INCREMENT,
+	depname VARCHAR(20) NOT NULL,
+	deinfo VARCHAR(50)
+);
+CREATE TABLE employee(
+	empid INT PRIMARY KEY AUTO_INCREMENT,
+	`name` VARCHAR(20) NOT NULL,
+	sex CHAR(1) NOT NULL DEFAULT '男',
+	title VARCHAR(20) NOT NULL,
+	birthday DATE NOT NULL,
+	depid INT,
+	CONSTRAINT fk_eid_did FOREIGN KEY(depid) REFERENCES department(depid)
+);
+CREATE TABLE salary(
+	empid INT,
+	basesalary DECIMAL(10, 2),
+	titleSalary DECIMAL(10, 2),
+	decuction DECIMAL(10, 2)
+);
+#3添加外键并设置级联更新、级联删除
+ALTER TABLE salary ADD CONSTRAINT fk_sal_eid FOREIGN KEY(empid) 
+REFERENCES employee(empid) ON UPDATE CASCADE ON DELETE CASCADE;
+#4插入记录
+INSERT INTO department()
+VALUES
+(111, '生产部', NULL),
+(222, '销售部', NULL),
+(333, '人事部', NULL);
+
+INSERT INTO employee()
+VALUES
+(1001, '张三', '男', '高级工程师', '1975-1-1', 111),
+(1002, '李四', '女', '助工', '1985-1-1', 111),
+(1003, '王五', '男', '工程师', '1978-11-11', 222),
+(1004, '赵六', '男', '工程师', '1999-1-1', 222);
+
+INSERT INTO salary()
+VALUES
+(1001, 2200, 1100, 200),
+(1002, 1200, 200, NULL),
+(1003, 2900, 700, 200),
+(1004, 1950, 700, 150);
+```
+