使用IF条件的MySQL更新 [英] MySQL UPDATE using IF condition

问题描述

我什至不确定这是否可行，但是如果满足特定条件，我将尝试执行其他UPDATE.

I'm not even sure if this is possible but I'm trying to do different UPDATE if a certain condition is met.

用户[id，开始日期(NOT NULL)，结束日期(NULL)，原因(NULL)，.....]

user [id, start_date(NOT NULL), end_date(NULL), reason(NULL), .....]

user_roles [id，role_id，user_id，start_date(NOT NULL)，end_date(NULL)]

user_roles [id, role_id, user_id, start_date(NOT NULL), end_date(NULL)]

我现在所拥有的是这个，但是只有在用户存在角色并且其end_date为NULL时，这才有效:

What I have right now is this but this only works if a role exists for the user and it's end_date is NULL:

UPDATE user p 
JOIN user_roles ur ON p.id = ur.user_id 
SET ur.end_date = NOW()
   , p.end_date = NOW()
   , p.reason = "Retired" 
WHERE p.id = 5 
AND ur.end_date IS NULL

我当时正在考虑做这样的事情:

I was thinking of doing something like this:

IF EXISTS (SELECT id FROM user_roles 
WHERE user_id = 5 AND end_date IS NULL)
THEN 
    UPDATE user p 
    JOIN user_roles ur ON p.id = ur.user_id 
    SET ur.end_date = NOW()
        , p.end_date = NOW()
        , p.reason = "Retired" 
    WHERE p.id = 5 AND ur.end_date IS NULL 
ELSE 
    UPDATE user 
    SET end_date = NOW()
        , reason = "Retired" 
    WHERE id = 5 
END IF

推荐答案

由于唯一的区别是您是将ur.end_Date设置为当前日期还是将其设置为现有日期? /p>

Since the only difference is whether you are setting ur.end_Date to either the current Date or setting it to it's existing date could you not just use the following:

UPDATE user p  
JOIN user_roles ur 
ON p.id = ur.user_id  
SET 
ur.end_date = IF (ur.end_date IS NULL, NOW(), ur.end_date),
p.end_date = NOW(), 
p.reason = "Retired" 
WHERE p.id = 5

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