具有条件聚合的一对多查询以及如何从查询中检索不同的结果

Question

一位成员向我提供了解决方案，结果如下：

SELECT s.StampId 
   , ct.Country
   ,StatusTable.Status
   , MAX(case when q.statusId = 1 and q.MintUsedId = 1 then 'True' ELSE 'False' END) as HaveMNH
   , MAX(case when q.statusId = 1 and q.MintUsedId = 2 then 'True' ELSE 'False' END) as HaveMH 
   , MAX(case when q.statusId = 1 and q.MintUsedId = 3 then 'True' ELSE 'False' END) as HaveUsed
   , MAX(case when q.statusId = 2 and q.MintUsedId = 1 then 'True' ELSE 'False' END) as WantMNH
   , MAX(case when q.statusId = 2 and q.MintUsedId = 2 then 'True' ELSE 'False' END) as WantMH 
   , MAX(case when q.statusId = 2 and q.MintUsedId = 3 then 'True' ELSE 'False' END) as WantUsed
   , MAX(case when q.statusId = 3 and q.MintUsedId = 1 then 'True' ELSE 'False' END) as TradeMNH
   , MAX(case when q.statusId = 3 and q.MintUsedId = 2 then 'True' ELSE 'False' END) as TradeMH 
   , MAX(case when q.statusId = 3 and q.MintUsedId = 3 then 'True' ELSE 'False' END) as TradeUsed
FROM StampTable s
LEFT JOIN StampQuantatiesTable sq ON s.StampId = sq.StampId
LEFT JOIN QuantatiesTable q ON q.QuantatiesId = sq.QuantatiesId
left Join CountryTable ct on S.Country = ct.CountryId
Left Join StatusTable on q.StatusId= StatusTable.StatusId
GROUP BY s.StampId 
       , ct.Country
       ,StatusTable.Status

在我的数据库中，邮票可能位于 none 或 3 个 statusid 组的任意组合中。对我来说，这些群体代表“拥有”、“想要”和“交易”。

如果我只在其中一个组中包含一个 WHERE 语句说“有”，我会得到正确的结果，但如果我对两个或更多组执行相同的操作，我会得到重复的结果。

我的问题是如何限制返回的结果，使其不包含重复项。

提前感谢您的帮助。

Answer 1

您对 q.statusid 进行了条件聚合，而 q.statusid 又与 StatusTable.StatusId 相结合，因此对于相同的 s.stampid, ct.Country

，您的 StatusTable.Status 可能会有所不同

您不应在 group by 和 select 子句中使用 StatusTable.Status（尽管您可以在 select 中的 StatusTable.Status 上使用聚合函数条款）

使用以下查询：

SELECT s.StampId 
   , ct.Country
   -- ,StatusTable.Status -- or max, min, etc aggregate function on StatusTable.Status
   , MAX(case when q.statusId = 1 and q.MintUsedId = 1 then 'True' ELSE 'False' END) as HaveMNH
   , MAX(case when q.statusId = 1 and q.MintUsedId = 2 then 'True' ELSE 'False' END) as HaveMH 
   , MAX(case when q.statusId = 1 and q.MintUsedId = 3 then 'True' ELSE 'False' END) as HaveUsed
   , MAX(case when q.statusId = 2 and q.MintUsedId = 1 then 'True' ELSE 'False' END) as WantMNH
   , MAX(case when q.statusId = 2 and q.MintUsedId = 2 then 'True' ELSE 'False' END) as WantMH 
   , MAX(case when q.statusId = 2 and q.MintUsedId = 3 then 'True' ELSE 'False' END) as WantUsed
   , MAX(case when q.statusId = 3 and q.MintUsedId = 1 then 'True' ELSE 'False' END) as TradeMNH
   , MAX(case when q.statusId = 3 and q.MintUsedId = 2 then 'True' ELSE 'False' END) as TradeMH 
   , MAX(case when q.statusId = 3 and q.MintUsedId = 3 then 'True' ELSE 'False' END) as TradeUsed
FROM StampTable s
LEFT JOIN StampQuantatiesTable sq ON s.StampId = sq.StampId
LEFT JOIN QuantatiesTable q ON q.QuantatiesId = sq.QuantatiesId
left Join CountryTable ct on S.Country = ct.CountryId
Left Join StatusTable on q.StatusId= StatusTable.StatusId
GROUP BY s.StampId 
       , ct.Country
      -- ,StatusTable.Status

具有条件聚合的一对多查询以及如何从查询中检索不同的结果

One-to-many query with conditional aggregation and how to retrieve distinct results from query

sql

sql-server-express