SQL 子查询替代 INTERSECT

Question

我有两张桌子： P 和 PC （由 Id 列连接的主/详细信息）

Table P:
Id integer
Name varchar(12)

Table PC:
Id   integer
Code varchar(12)
Val  number

我想从 P 中获取满足以下同时条件的所有名称：

• 拥有一台带有 < code>PC.Code='A' 和 Val>100

• 有另一台 PC 具有 PC.Code='B' 和 Val>80

总之，我只对那些详细信息符合这两个条件的 P.Name 感兴趣。有没有一种方法可以在不使用 INTERSECT 的情况下进行选择？

INTERSECT 查询是：（

Select P.Name 
  from P, PC
 where P.Id=PC.Id
   and PC.Code='A' and Val>100
INTERSECT
Select P.Name 
  from P, PC
 where P.Id=PC.Id
   and PC.Code='B' and Val>80

兴趣是检查性能并允许查询在 Access 中运行）

Answer 1

不知道性能怎么样..试试吧..

SELECT P.Name 
  FROM P
  INNER JOIN PC AS a ON P.Id=a.Id and a.Cod='A' and a.Val>100
  INNER JOIN PC AS b ON P.Id=b.Id and a.Cod='B' and a.Val>80

Answer 2

这是一种在关系上等效的替代方法（即消除重复行）：

SELECT P.Name 
  FROM P
 WHERE EXISTS (
               SELECT * 
                 FROM PC
                WHERE P.Id = PC.Id
                      AND PC.Code ='A' 
                      AND PC.Val > 100
              )
      AND EXISTS (
                  SELECT * 
                    FROM PC
                   WHERE P.Id = PC.Id
                         AND PC.Code ='B' 
                         AND PC.Val > 80
                 );

以下是几个在语义上等效的替代方法（因为它们可能返回重复行）：

SELECT P.Name 
  FROM P, PC
 WHERE P.Id = PC.Id
       AND PC.Code ='A' 
       AND PC.Val > 100
       AND P.Name IN (
                      SELECT P1.Name 
                        FROM P AS P1, PC AS PC1
                       WHERE P1.Id = PC1.Id
                         AND PC1.Code = 'B' 
                             AND PC1.Val > 80
                     );
SELECT P.Name 
  FROM P, PC
 WHERE P.Id = PC.Id
       AND PC.Code ='A' 
       AND PC.Val > 100
       AND P.Name = ANY (
                         SELECT P1.Name 
                           FROM P AS P1, PC AS PC1
                          WHERE P1.Id = PC1.Id
                            AND PC1.Code = 'B' 
                                AND PC1.Val > 80
                        );

Answer 3

SELECT P.Name
  FROM P
  JOIN PC AS P1 ON P.Id = P1.Id AND P1.Cod = 'A' AND P1.Val > 100
  JOIN PC AS P2 ON P.Id = P2.Id AND P2.Cod = 'B' AND P2.Val >  80

使用表别名 P1 和 P2 允许您进行 3 路联接。不过，这并不完全是自连接。这次不行。

Answer 4

Select P.Name 
  from P, PC
 where P.Id=PC.Id
   and PC.Cod='A' and Val>100
   and exists (Select 1 From PC Where Id = P.Id and Cod = 'B' and Val > 80)

Answer 5

Select p.Name
from P p
inner join PC pc1 on p.Id = pc1.Id and pc1.Cod = 'A' and pc1.Val > 100
inner join PC pc2 on p.Id = pc2.Id and pc2.Cod = 'B' and pc2.Val > 80

Answer 6

实际上不会使用这个，而是替代方案...

SELECT P.Name
FROM   P
       JOIN PC
         ON P.Id = PC.Id
WHERE  PC.Cod IN ( 'A', 'B' )
       AND Val > 80
GROUP  BY P.Id,
          P.Name
 HAVING MAX(CASE WHEN PC.Cod='A' and Val>100 THEN 1 END) = 1 
 AND MAX(CASE WHEN PC.Cod='B' and Val>80 THEN 1 END) = 1 

或者对于 Microsoft Access，having 子句需要是

 HAVING MAX(IIf(PC.Cod='A' and Val>100, 1, 0)) = 1 
 AND MAX(IIf(PC.Cod='B' and Val>80, 1, 0)) = 1