Mysql update select结合使用

Update基本用法

UPDATE table_name
SET column1=value1,
	column2=value2,
	...
WHERE some_column = some_value;

重点：若不加where条件则是更新表中的所有数据

Update与Select结合

用法模板：

UPDATE T1
[INNER JOIN | LEFT JOIN] T2 ON T1.C1 = T2. C1
SET T1.C2 = T2.C2, 
    T2.C3 = expr
WHERE condition

示例：

UPDATE sys_user_copy sc
	INNER JOIN jianshe js ON sc.nick_name = js.`姓名`
						 AND sc.phonenumber = js.`手机号`
SET sc.user_sys = js.`登录名`
WHERE
	sc.user_sys is null