Question

如何重写以下查询，以使子查询成为联接的一部分？还是其他更好的方法？

Declare @CR varchar(32)

SELECT count(*)
FROM [dbo].[TableC]
    INNER JOIN  [dbo].[TableCS] ON [TableCS].[CSI] = [TableC].[CSI]
    INNER JOIN [dbo].[TableI] ON [TableI].TableIId = [TableC].[TableIId]
WHERE [TableC].[CR] = @CR
    AND [TableI].[POR] = (SELECT POR FROM TableI inner join [TableC] on TableI.TableIId =  [TableC].TableIId and [TableC].CR = @CR)
    AND [TableCS].[Consider] = 1

Answer 1

您应该能够使用别名将子查询转换为您的主查询...

SELECT
  COUNT(*) 
FROM
  [dbo].[TableC]
INNER JOIN 
  [dbo].[TableCS]
    ON [TableCS].[CSI] = [TableC].[CSI]
INNER JOIN
  [dbo].[TableI]
    ON [TableI].TableIId = [TableC].[TableIId]
(
    TableI   AliasedTableI
  INNER JOIN
    TableC   AliasedTableC
      ON  AliasedTableI.TableIId = AliasedTableC.TableIId
      AND AliasedTableC.CR       = @CR
)
  ON  AliasedTableI.POR = TableI.POR
WHERE
      [TableC].[CR] = @CR
  AND [TableCS].[ConsiderInExistenceChecks] = 1

这不可能是最好的也是最后的重构。但是，不知道您的模式或业务规则是我唯一可以为您编写的安全模式。

Answer 2

如果POR是TableC的列，那么...

Declare @CR varchar(32)

SELECT count(*)
        FROM [dbo].[TableC]
        INNER JOIN  [dbo].[TableCS] ON [TableCS].[CSI] = [TableC].[CSI]
        INNER JOIN [dbo].[TableI] ON [TableI].TableIId = [TableC].[TableIId] and [TableC].CR = @CR AND [TableI].[POR]= [TableC].POR
        WHERE [TableC].[CR] = @CR
        AND [TableCS].[Consider] = 1

用SQL中的Join替换子查询

2 个答案: