sql - 访问查询以合并字段表单相关表

Question

所以，假设我有桌子Product：

ProdID | ProdDesc
-----------------
     1 | Widget
     2 | Snikt Spring
     3 | Water Bearing

和表ProdFeature

ProdID | DocID | ProdSafe | ProdShiny
-------------------------------------
     1 |    34 | Y        | Null
     1 |    17 | Null     | Y
     2 |    54 | Y        | Null
     3 |     2 | Null     | Y

我将如何得到如下结果：

ProdID | ProdSafe | SafetyDocID | ProdShiny | ShinyDocID
--------------------------------------------------------
     1 | Y        |          34 | Y         |         17

任何帮助表示赞赏。~R

Answer 1

类似的东西？

SELECT p.ProdID,
       pf1.ProdSafe,
       pf1.DocID SafetyDocID,
       pf2.ProdShiny,
       pf2.DocID ShinyDocID
  FROM Product p
           left outer join ProdFeature pf1
               on p.ProdID = pf1.ProdID and pf1.ProdSafe is not null
           left outer join ProdFeature pf2
               on p.ProdID = pf2.ProdID and pf2.ProdShiny is not null

这是一个演示。

另一个性能较低的版本：

SELECT p.ProdID,
       (select ProdSafe
          from ProdFeature
         where ProdID = p.ProdID
               and ProdSafe is not null) ProdSafe,
       (select DocID
          from ProdFeature
         where ProdID = p.ProdID
               and ProdSafe is not null) SafetyDocID,
       (select ProdShiny
          from ProdFeature
         where ProdID = p.ProdID
               and ProdShiny is not null) ProdShiny,
       (select DocID
          from ProdFeature
         where ProdID = p.ProdID
               and ProdShiny is not null) ShinyDocID
  FROM Product p

这是一个演示。