合并两个select语句的结果

Question

我正在使用带有ASP.NET的T-SQL,而c#和我对SQL很新.

我想知道如何结合两个查询的结果

查询1:

SELECT tableA.Id,  tableA.Name, [tableB].Username AS Owner, [tableB].ImageUrl, [tableB].CompanyImageUrl, COUNT(tableD.UserId) AS NumberOfUsers
 FROM tableD RIGHT OUTER JOIN 
         [tableB] INNER JOIN
         tableA ON [tableB].Id = tableA.Owner ON tableD.tableAId = tableA.Id
 GROUP BY tableA.Name, [tableB].Username, [tableB].ImageUrl, [tableB].CompanyImageUrl

QUERY2:

 SELECT tableA.Id,  tableA.Name, COUNT([tableC].Id) AS NumberOfPlans
 FROM   [tableC] RIGHT OUTER JOIN
           tableA ON [tableC].tableAId = tableA.Id
 GROUP BY tableA.Id, tableA.Name

任何帮助将非常感激.提前致谢

Answer 1

你可以使用联盟.

这将在单独的行中返回查询结果.

首先,您必须确保两个查询都返回相同的列.

然后你可以这样做:

SELECT tableA.Id, tableA.Name, [tableB].Username AS Owner, [tableB].ImageUrl, [tableB].CompanyImageUrl, COUNT(tableD.UserId) AS Number
FROM tableD 
RIGHT OUTER JOIN [tableB] 
INNER JOIN tableA ON [tableB].Id = tableA.Owner ON tableD.tableAId = tableA.Id 
GROUP BY tableA.Name, [tableB].Username, [tableB].ImageUrl, [tableB].CompanyImageUrl

UNION

SELECT tableA.Id, tableA.Name,  '' AS Owner, '' AS ImageUrl, '' AS CompanyImageUrl, COUNT([tableC].Id) AS Number
FROM 
[tableC] 
RIGHT OUTER JOIN tableA ON [tableC].tableAId = tableA.Id GROUP BY tableA.Id, tableA.Name

如前所述,两个查询都返回完全不同的数据.如果两个查询都返回可能被认为相似的数据,您可能只想这样做.

所以

您可以使用加入

如果在两个查询之间共享某些数据.这会将两个查询的结果放入由id连接的单个行中,这可能更像是你想要在这里做的...

你可以这样做:

SELECT tableA.Id, tableA.Name, [tableB].Username AS Owner, [tableB].ImageUrl, [tableB].CompanyImageUrl, COUNT(tableD.UserId) AS NumberOfUsers, query2.NumberOfPlans
FROM tableD 
RIGHT OUTER JOIN [tableB] 
INNER JOIN tableA ON [tableB].Id = tableA.Owner ON tableD.tableAId = tableA.Id 


INNER JOIN 
  (SELECT tableA.Id, COUNT([tableC].Id) AS NumberOfPlans 
   FROM [tableC] 
   RIGHT OUTER JOIN tableA ON [tableC].tableAId = tableA.Id 
   GROUP BY tableA.Id, tableA.Name) AS query2 
ON query2.Id = tableA.Id

GROUP BY tableA.Name, [tableB].Username, [tableB].ImageUrl, [tableB].CompanyImageUrl

Answer 2

虽然可以将结果结合起来,但我建议不要这样做.

您有两种根本不同类型的查询,它们返回不同数量的行,不同数量的列和不同类型的数据.最好保持原样 - 两个单独的查询.

Answer 3

您可能使用支持公用表表达式(CTE)的Microsoft SQL Server(请参阅http://msdn.microsoft.com/en-us/library/ms190766.aspx),它们非常适合查询优化.所以我建议你帮忙施工:

WITH GetNumberOfPlans(Id,NumberOfPlans) AS (
    SELECT tableA.Id, COUNT(tableC.Id)
    FROM tableC
        RIGHT OUTER JOIN tableA ON tableC.tableAId = tableA.Id
    GROUP BY tableA.Id
),GetUserInformation(Id,Name,Owner,ImageUrl,
                     CompanyImageUrl,NumberOfUsers) AS (
    SELECT tableA.Id, tableA.Name, tableB.Username AS Owner, tableB.ImageUrl,
        tableB.CompanyImageUrl,COUNT(tableD.UserId),p.NumberOfPlans
    FROM tableA
        INNER JOIN tableB ON tableB.Id = tableA.Owner
        RIGHT OUTER JOIN tableD ON tableD.tableAId = tableA.Id
    GROUP BY tableA.Name, tableB.Username, tableB.ImageUrl, tableB.CompanyImageUrl
)
SELECT u.Id,u.Name,u.Owner,u.ImageUrl,u.CompanyImageUrl
    ,u.NumberOfUsers,p.NumberOfPlans
FROM GetUserInformation AS u
    INNER JOIN GetNumberOfPlans AS p ON p.Id=u.Id

在完成CTE的一些经验之后,您会发现使用CTE编写代码非常容易,您会对性能感到满意.