计算字段中的MySQL IF条件 [英] MySQL IF Condition in a Calculated Field

问题描述

我正在尝试创建一个计算字段，如果两个值恰好相同，则值会加倍。我在变量MY中编码这个条件。我是SQL的新手，所以我道歉。

I am trying to create a calculated field where if two values happen to be the same, the value doubles. I am coding this condition in the variable MY. I am new to SQL, so I apologize.

这是我的尝试：

SELECT EXPERT_SCORE*MY
IF(CONSUMER_EXPERT_SCORE_ID= CONSUMER_EXPERT_ID, 1, -1) AS MY 
FROM consumer_expert_score
WHERE CONSUMER_EXPERT_SCORE_ID=2 OR 1;

提前致谢！

推荐答案

您需要CASE WHEN和IN（）子句。

You want CASE WHEN, and the IN ( ) clause.

不幸的是我无法完全重写你的查询，因为你的条件是重言式，它总会返回1.也许你的意思是别的？无论如何，我把它改成了一些我认为你的意思：

Unfortunately I could not rewrite your query completely because your conditional is a tautology, it will always return 1. Maybe you meant something else? Anyway, I changed it up a bit to what I think you might have meant:

SELECT ....
  case when consumer_expert_id = 1 then 1 else -1 end as my
  from consumer_expert_score
 where consumer_expert_score_id IN (2,1)

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