如何在SQL查询中两次使用CASE子句

Question

I am trying to apply two conditions in one SQL Query.

(select DISTINCT (
        CASE WHEN (
         ABC.GemUserID = '99' ) 
         OR ABC.GemUserID != '99'
            THEN 'Yes'
    ELSE 'No'
        END)) AS AllWell

This gives me output as "Yes" where as the CASE is true only for 1 file like below :

Current Result:

99 , Yes
99 , Yes
99 , Yes

Expected Result:

99 , No
99 , No
99 , Yes

I am using the below query but the SQL Query Intellisence is identifying it as wrong.

Wrong Query:

(select DISTINCT (
    CASE WHEN ( ABC.GEMUserID  = '99' THEN 'Yes' else 'No'
    CASE WHEN ( ABC.GEMUserID != '99' THEN 'No'  else 'Yes'

    END)) AS AllWell

After fixing the above Wrong Query:

(select DISTINCT 
        (CASE WHEN  ABC.GemUserID  = '99' THEN 'Yes' else 'No' END), 
        (CASE WHEN  ABC.GemUserID != '99' THEN 'No'  else 'Yes' END))
         AS AllWell

But I am getting error:

Msg 116, Level 16, State 1, Line 17 Only one expression can be specified in the select list when the subquery is not introduced with EXISTS.

How to fix this?

Answer 1

select distinct is -- itself -- part of SQL syntax. The distinct is not a function. It should not be followed by parentheses. So, if I understand your question:

select DISTINCT 
       ( CASE WHEN ABC.GEMUserID = '99' THEN 'Yes' else 'No' END),
       ( CASE WHEN ABC.GEMUserID <> '99' THEN 'No'  else 'Yes' END) as AllWell

Do you plan on giving the first column a name?

Answer 2

select DISTINCT 
CASE WHEN  ABC.GEMUserID  = '99' THEN 'Yes' 
     ELSE 'No' -- This is automatically When ABC.GEMUserID <> '99'
END AS AllWell

Answer 3

According to the error, your query is a subquery (probably behind IN?) in a larger SQL command. Therefore, it is not possible for such subquery to return more than one column .

Answer 4

So your first query, you've said:

CASE WHEN userID = 99 OR userID != 99

In other words:

CASE WHEN 1=1

This is why it returns yes for everything (not sure what the difference between your current and expected result should be considering that the userID is 99 for all rows).

For your erroneous query, seems you're returning that select in the middle of another select (since you alias it at the end). Due to that, you cannot return more than one column in your nested select. You do not need the second CASE statement, simply change your query to:

(select DISTINCT
    CASE WHEN ABC.GemUserID = '99' THEN 'Yes' Else 'No' End) AS AllWell

Assuming that you hold the missing pieces to the query such as the FROM.