在同一个字段上使用大小写更新值

Question

我想在MySQL中使用大小写更新语句，但它不会更改任何值。

该查询不会给出任何错误，但有0个受影响的行。

UPDATE `tablename` 
SET `type` = (
    CASE 
     WHEN `type` = 1 THEN 1 
     WHEN `type` = 2 THEN 2 
     WHEN `type` = 3 THEN 19 
     WHEN `type` = 4 THEN null 
     WHEN `type` = 5 THEN null 
     WHEN `type` = 6 THEN 81 
     WHEN `type` = 7 THEN null 
     WHEN `type` = 8 THEN 22 
     WHEN `type` = 9 THEN 21 
     WHEN `type` = 10 THEN 78 
     WHEN `type` = 11 THEN 80 
     WHEN `type` = 12 THEN 79 
    END) 
WHERE user_id IS NOT NULL; 

任何人都知道我可以解决这个问题。

Answer 1

尝试移动type后Case。

UPDATE `tablename` 
SET `type` = 
    CASE `type` 
     WHEN 1 THEN 1 
     WHEN 2 THEN 2 
     WHEN 3 THEN 19 
     WHEN 4 THEN null 
     WHEN 5 THEN null 
     WHEN 6 THEN 81 
     WHEN 7 THEN null 
     WHEN 8 THEN 22 
     WHEN 9 THEN 21 
     WHEN 10 THEN 78 
     WHEN 11 THEN 80 
     WHEN 12 THEN 79 
    END 
WHERE user_id IS NOT NULL; 

Answer 2

UPDATE test 
SET `password` = (
CASE 
    WHEN `password` = 1 THEN 'one' 
    WHEN `password` = 2 THEN 'two' 
    WHEN `password` = 3 THEN 'three' 
    WHEN `password` = 4 THEN null 
    WHEN `password` = 5 THEN null 
    WHEN `password` = 6 THEN 81 
    WHEN `password` = 7 THEN null 
END) 
where userindex=1 

工作完全正常，我。我manuplated它适合我的测试数据..kindly remanuplate值，然后再试一次。

还检查您是否有任何用户不为空user_id

Answer 3

查询看起来不错。建议使用select来尝试是否会返回任何记录。

SELECT *, CASE 
     WHEN `type` = 1 THEN 1 
     WHEN `type` = 2 THEN 2 
     WHEN `type` = 3 THEN 19 
     WHEN `type` = 4 THEN null 
     WHEN `type` = 5 THEN null 
     WHEN `type` = 6 THEN 81 
     WHEN `type` = 7 THEN null 
     WHEN `type` = 8 THEN 22 
     WHEN `type` = 9 THEN 21 
     WHEN `type` = 10 THEN 78 
     WHEN `type` = 11 THEN 80 
     WHEN `type` = 12 THEN 79 
    END as test 
FROM `tablename` WHERE user_id IS NOT NULL