1. 指定数据库
mysql> use portal;
2. 数据库表基本操作
2.1 查看数据表
mysql> show tables;
3. 创建表
3.1 创建表语法
语法:
CREATE TABLE table_name (column_name column_type);
示例:
mysql> CREATE TABLE product
-> (
-> ProductID INT,
-> ProductName VARCHAR(50)
-> );
3.2 设置主键
单字段主键:
column_name column_type PRIMARY KEY
mysql> CREATE TABLE Product
-> (
-> ProductID INT PRIMARY KEY,
-> ProductName VARCHAR(50)
-> );
多字段主键:
PRIMARY KEY (column_name, ... , column_name)
mysql> CREATE TABLE Product
-> (
-> ProductID INT,
-> CategoryID INT,
-> ProductName VARCHAR(50),
-> PRIMARY KEY (ProductID,CategoryID)
-> );
3.3 设置外键
语法:
CONSTRAINT constraint_name FOREIGN KEY(column_name, ... , column_name) REFERENCES table_name(column_name, ... ,column_name)
示例:
mysql> CREATE TABLE category
-> (
-> CategoryID INT PRIMARY KEY,
-> CategoryName VARCHAR(50)
-> );
mysql> CREATE TABLE product
-> (
-> ProductID INT PRIMARY KEY,
-> ProductName VARCHAR(50),
-> CategoryID INT,
-> CONSTRAINT FK_product_category FOREIGN KEY(CategoryID) REFERENCES category(CategoryID)
-> );
3.4 设置非空约束
语法:
column_name column_type NOT NULL
示例:
mysql> CREATE TABLE product
-> (
-> ProductID INT PRIMARY KEY,
-> ProductName VARCHAR(50) NOT NULL
-> );
3.5 设置唯一约束
语法:
column_name column_type unique
示例:
mysql> CREATE TABLE product
-> (
-> ProductID INT PRIMARY KEY,
-> ProductName VARCHAR(50) UNIQUE
-> );
3.6 设置字段值自动增加
语法:
column_name column_type AUTO_INCREMENT
示例:
mysql> CREATE TABLE product
-> (
-> ProductID INT AUTO_INCREMENT PRIMARY KEY,
-> ProductName VARCHAR(50)
-> );
3.7 设置字段默认值
语法:
column_name column_type DEFAULT default_value
示例:
mysql> CREATE TABLE product
-> (
-> ProductID INT PRIMARY KEY AUTO_INCREMENT,
-> ProductName VARCHAR(50),
-> UnitPrice FLOAT DEFAULT 0
-> );
4. 查看表
4.1 查看表基本结构语句 DESC
语法:
DESC table_name
示例:
mysql> DESC product;
+-------------+-------------+------+-----+---------+----------------+
| Field | Type | Null | Key | Default | Extra |
+-------------+-------------+------+-----+---------+----------------+
| ProductID | int(11) | NO | PRI | NULL | auto_increment |
| ProductName | varchar(50) | YES | | NULL | |
| UnitPrice | float | YES | | 0 | |
+-------------+-------------+------+-----+---------+----------------+
3 rows in set (0.02 sec)
4.2 查看表详细结构语句SHOW CREATE TABLE
语法:
SHOW CREATE TABLE table_name;
示例:
mysql> SHOW CREATE TABLE product;
5. 修改表
5.1 修改表名
语法:
ALTER TABLE old_table_name RENAME [TO] new_table_name;
示例:
mysql> ALTER TABLE product RENAME product1;
5.2 修改字段数据类型
语法:
ALTER TABLE table_name MODIFY column_name column_type
示例:
mysql> ALTER TABLE product MODIFY ProductName VARCHAR(100);
mysql> ALTER TABLE product MODIFY ProductName VARCHAR(100) NOT NULL;
5.3 修改字段名
语法:
ALTER TABLE table_name CHANGE old_column_name new_column_name new_column_type
示例:
mysql> ALTER TABLE product CHANGE ProductName Name VARCHAR(50);
5.4 增加字段
语法:
ALTER TABLE table_name ADD column_name column_type [CONSTRAINT] [FIRST | AFTER column_name];
示例:
mysql> ALTER TABLE product ADD UnitPrice FLOAT NOT NULL;
mysql> ALTER TABLE product ADD ID INT NOT NULL FIRST;
mysql> ALTER TABLE product ADD ProductNo VARCHAR(50) NOT NULL AFTER ProductID;
5.5 删除字段
语法:
ALTER TABLE table_name DROP column_name;
示例:
mysql> ALTER TABLE product DROP ID;
5.6 修改字段排列位置
语法:
ALTER TABLE table_name MODIFY column_name column_type FIRST | AFTER colunm_name;
示例:
mysql> ALTER TABLE product MODIFY ProductNo VARCHAR(50) FIRST;
mysql> ALTER TABLE product MODIFY ProductNo VARCHAR(50) AFTER ProductID;
5.7 修改表存储引擎
语法:
ALTER TABLE table_name ENGINE=engine_name;
示例:
mysql> ALTER TABLE product ENGINE=MyISAM;
mysql> SHOW CREATE TABLE product\G;
5.8 删除表的外键约束
语法:
ALTER TABLE table_name DROP FOREIGN KEY constraint_name;
示例:
mysql> ALTER TABLE product DROP FOREIGN KEY FK_product_category;
6. 删除表
语法:
DROP TABLE table_name ;
示例:
mysql> DROP TABLE product;