mysql-update、delete、select操作。

1、单表更新记录UPDATE

UPDATE [LOW_PRIORITY][IGNORE]table_reference SET col_name1 = {expr1|DEFAULT}[,col_name2...]...[WHERE where_conditinion]

例子：

1、更新一列

UPTATE users SET age = age +5;

2、更新多列

UPDATE users SET age = age - id,sex = 0;

3、条件更新，如更新偶数列

UPTATE users SET age = age +5 WHERE id%2 = 0;

2、单表删除DELETE

DELETE FROM tb_name [WHERE where_condition]

例子：

DELETE FROM users where id = 1;

3、查询表达式解析

4、WHERE 语句进行条件查询

5、group by对查询结果分组

例子：

SELECT sex FROM users GROUP BY sex;

6、HAVING 语句设置分组条件

SELECT sex,age FROM users GROUP BY sex HAVING age > 10;

注意，having条件必须存在于查询的东西当中

7、order by 对查询结果进行排序

8、limit限制查询数量