mysql - WHERE EXISTS mysql查询错误

Question

SET @userID := 1;
SELECT 1 AS isSmoker WHERE EXISTS (SELECT SituationID 
                                     FROM usersituation 
                                    WHERE UserID=@userID
                                      AND SituationID=3);

SQL查询:

 SELECT 1 AS isSmoker WHERE EXISTS (SELECT SituationID 
                                      FROM usersituation 
                                     WHERE UserID=@userID 
                                       AND SituationID=3) 

MySQL said:

1064 - You have an error in your SQL syntax; check the manual that corresponds to your MySQL server version for the right syntax to use near 'WHERE EXISTS ( SELECT SituationID FROM usersituation WHERE UserID=@userID AND ' at line 1

这是我收到的错误，但我不知道为什么会这样。

SELECT SituationID FROM `usersituation` WHERE UserID=@userID AND SituationID=3

单独使用时返回一行。

注意:

The purpose of the Query is, if the subquery returns any value then return one row with the value of 1 in a custom column named isSmoker

Answer 1

SET @userID := 1;
SELECT 1 AS isSmoker from usersituation WHERE EXISTS ( SELECT SituationID FROM usersituation WHERE UserID=@userID AND SituationID=3);

你可以试试上面的代码。

在这里您忘记了 from 关键字。