mysql 增删改查最基本用法小结

目录：

　　1.新建数据库
　　2.新建数据表
　　3.查看表结构
　　4.增删改查

　建立一个数据库students
　建立一块数据表class1
　　内容包括：

　　id 主键 自动编号 无符号位 SMALLINT类型
　　name VARCHAR(30)类型 非空 唯一值
　　school VARCHAR(30) 非空 默认值chengdu college

代码如下：
1.建立数据库

        mysql> CREATE DATABASE students;
        Query OK, 1 row affected (0.07 sec)

2.进入数据库

        mysql> USE students;
        Database changed

3.新建表

        mysql> CREATE TABLE class1 (
        -> id SMALLINT UNSIGNED AUTO_INCREMENT ,
        -> name VARCHAR(30) NOT NULL UNIQUE KEY ,
        -> school VARCHAR(30) DEFAULT 'chengdu_collage' ,
        -> PRIMARY KEY(id)
        -> );
        Query OK, 0 rows affected (0.09 sec)

4.查看表结构

        mysql> DESC class1;
        +--------+----------------------+------+-----+-----------------+----------------+
        | Field  | Type                 | Null | Key | Default         | Extra          |
        +--------+----------------------+------+-----+-----------------+----------------+
        | id     | smallint(5) unsigned | NO   | PRI | NULL            | auto_increment |
        | name   | varchar(30)          | NO   | UNI | NULL            |                |
        | school | varchar(30)          | YES  |     | chengdu_collage |                |
        +--------+----------------------+------+-----+-----------------+----------------+
        3 rows in set (0.00 sec)

1.插入(INSERT)

    1.INSERT INTO tb_name [(col_name...)] {VALUES|VALUE}({expr | DEFAULT},....),(...)...
        例子：
            mysql> INSERT INTO class1 (name) VALUES ('john');
            Query OK, 1 row affected (0.01 sec)
            
            mysql> INSERT INTO class1 VALUES (DEFAULT,'jobs','chengdu_agricultural_college');
            Query OK, 1 row affected (0.01 sec)
            
    
    2.INSERT INTO tb_name SET col_name = {expr | DEFAULT},...
        例子：
            mysql> INSERT INTO class1 SET name='tom';
            Query OK, 1 row affected (0.02 sec)
            
            mysql> INSERT INTO class1 SET name='lues',school='chengdu_agricultural_college';
            Query OK, 1 row affected (0.01 sec)

2.修改(UPDATE)

    1.UPDATE [LOW_PRIORITY] [IGNORE] table_reference
    SET col_name1={expr1|DEFAULT} [, col_name2={expr2|DEFAULT}] ...
    例子：
        mysql> UPDATE class1 
        -> SET name='lues2' WHERE name='lues';
        Query OK, 1 row affected (0.07 sec)
        Rows matched: 1  Changed: 1  Warnings: 0

3.删除(DELETE)

    1.DELETE [LOW_PRIORITY] [QUICK] [IGNORE] FROM tbl_name
      [WHERE where_condition]
      
    例子：
        mysql> DELETE FROM class1 WHERE name='lues2';
        Query OK, 1 row affected (0.01 sec)

4.查询(SELECT)

    1.简单查询
        mysql> SELECT * FROM class1;
        +----+------+------------------------------+
        | id | name | school                       |
        +----+------+------------------------------+
        |  1 | john | chengdu_collage              |
        |  2 | jobs | chengdu_agricultural_college |
        |  3 | tom  | chengdu_collage              |
        +----+------+------------------------------+
        3 rows in set (0.00 sec)
        
    2.简单的条件查询
        mysql> SELECT * FROM class1 WHERE id > 1;
        +----+------+------------------------------+
        | id | name | school                       |
        +----+------+------------------------------+
        |  2 | jobs | chengdu_agricultural_college |
        |  3 | tom  | chengdu_collage              |
        +----+------+------------------------------+
        2 rows in set (0.00 sec)
        
    3.简单的分组查询
        mysql> SELECT * FROM class1 GROUP BY school DESC;
        +----+------+------------------------------+
        | id | name | school                       |
        +----+------+------------------------------+
        |  1 | john | chengdu_collage              |
        |  2 | jobs | chengdu_agricultural_college |
        +----+------+------------------------------+
        2 rows in set (0.00 sec)
        
    4.简单的排序查询
        mysql> SELECT * FROM class1 ORDER BY id DESC;
        +----+------+------------------------------+
        | id | name | school                       |
        +----+------+------------------------------+
        |  3 | tom  | chengdu_collage              |
        |  2 | jobs | chengdu_agricultural_college |
        |  1 | john | chengdu_collage              |
        +----+------+------------------------------+
        3 rows in set (0.00 sec)