mysql 更新数据 update

update 语句用于在数据库表中修改数据
语法：

UPDATE table_name 
SET column_name = new_value
WHERE column_name = some_value;

例如：

UPDATE test1
SET firist_name = lilsa
WHERE user.city = london;

多表链接修改：

UPDATE test1
    INNER JOIN test2
    ON test1.id = test2.user_id
SET test1.is_admin=test2.is_admin
    WHERE test1.id<100;

等同于

UPDATE test1,test2
SET test1.is_admin=test2.is_admin
    WHERE test1.id = test2.user_id AND test1.id<100;

将一个表中某个字段的值赋给另一个表的字段：

UPDATE test1
SET score = score + 5
WHERE test1.id in (SELECT test1_id from test2 where s_id = 7);

UPDATE 也可以用left join、inner join来进行关联，执行效率会更高

UPDATE test1 t1 inner join test12 t2 on t1.id = t2.test1_id
SET score = score + 5
WHERE t2.s_id = 7;