mysql 更新數據 update

update 語句用於在數據庫表中修改數據
語法：

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;

多表鏈接修改：

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

等同於

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

將一個表中某個字段的值賦給另一個表的字段：

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來進行關聯，執行效率會更高

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