Question

所以我查询了以下where语句。基本上，我想确保在过去7天内没有运动或球员活动。

WHERE......   
AND (( (SELECT max(sportswagerbyleague.asOfDate) 
            FROM sportswagerbyleague 
            WHERE sportswagerbyleague.userID = customer_profile.userID)  
                <= date(CURDATE()) - INTERVAL 7 DAY  ) 
                AND ((SELECT max(pa.txndate) 
                    FROM player_activity pa 
                    WHERE pa.userID = customer_profile.userID) <= date(CURDATE()) - INTERVAL 7 DAY ) )

但是，如果存在NULL值（也就是说该用户没有玩家活动或体育活动），那么该特定用户的WHERE语句将变为false。我希望WHERE语句即使对于单个NULL值也保持为true。

建议？

Answer 1

将值与NULL值进行比较始终为false，因此您必须单独处理该情况。你可以为此目的使用IS NULL之类的东西。

Answer 2

转而使用NOT EXISTS来避免三值逻辑：

WHERE......   
AND NOT EXISTS
 ( SELECT *
   FROM sportswagerbyleague 
   WHERE sportswagerbyleague.userID = customer_profile.userID  
     AND sportswagerbyleague.asOfDate > date(CURDATE()) - INTERVAL 7 DAY
 ) 
AND NOT EXISTS
 (
   SELECT *max(pa.txndate) 
   FROM player_activity pa 
   WHERE pa.userID = customer_profile.userID
     AND pa.txndate > date(CURDATE()) - INTERVAL 7 DAY
 )

在where语句中处理NULL值（SQL）

2 个答案: