从子查询中获取多个值的解决方法答案

【问题标题】：workaround for getting multiple values from subquery从子查询中获取多个值的解决方法
【发布时间】：2014-01-12 23:57:08
【问题描述】：

这是我的 sql 查询：

SELECT c.*, CAST ( 0 as int ) Score 
FROM Caregiver c JOIN Elderly e ON EXISTS 
( 
 SELECT x.LanguageID FROM 
 ( 
  SELECT 1 AS LanguageID WHERE e.Chinese = 1 UNION ALL 
  SELECT 2 AS LanguageID WHERE e.Malay = 1 UNION ALL 
  SELECT 3 AS LanguageID WHERE e.Tamil = 1 UNION ALL 
  SELECT 4 AS LanguageID WHERE e.English = 1 UNION ALL 
  SELECT 5 AS LanguageID WHERE e.Others = 1
 ) 
 x INTERSECT SELECT y.LanguageID FROM 
 ( 
  SELECT 1 AS LanguageID WHERE c.Chinese = 1 UNION ALL 
  SELECT 2 AS LanguageID WHERE c.Malay = 1 UNION ALL 
  SELECT 3 AS LanguageID WHERE c.Tamil = 1 UNION ALL 
  SELECT 4 AS LanguageID WHERE c.English = 1 UNION ALL 
  SELECT 5 AS LanguageID WHERE c.Others = 1
 ) 
 y 
) 
WHERE e.NRIC=@nric2 
AND c.CaregiverID != (SELECT CaregiverID FROM RequestPairing WHERE ReqID=@reqid2)

这不起作用，因为子查询 ( SELECT CaregiverID FROM RequestPairing WHERE ReqID=@reqid2) 返回多个值。

我的目的是利用子查询将某些行排除在主查询返回之外。

那么有什么解决方法吗？

【问题讨论】：

标签： sql sql-server-2012 subquery

【解决方案1】：

我想你想要not in:

WHERE e.NRIC=@nric2 and
      c.CaregiverID not in (SELECT CaregiverID FROM RequestPairing WHERE ReqID=@reqid2)

【讨论】：

thx，not in 和 not exists 都有效，但我选择 not exists，因为性能显然更好。

【解决方案2】：

您可以将此条件更改为NOT EXISTS：

WHERE e.NRIC=@nric2 
AND NOT EXISTS (SELECT CaregiverID FROM RequestPairing 
WHERE ReqID=@reqid2 AND CaregiverID = c.CaregiverID)

【讨论】：

【解决方案3】：

是的。除了!=，您可以使用NOT IN 在选择查询周围加上括号。

【讨论】：