sql - 内连接在最后一个连接中有多个 ON 子句

Question

我正在维护 OLD sql 数据库，我有一个像这样的 select 子句:

SELECT
              [P].[ItemID]
            , SUM([p].[OnOrder]) AS [OnOrder]
            , [I].[FullName] AS [PartNo]
            , [I].[PurchaseDesc] AS [Description]
            , [I].[ItemCust3]
              FROM @POItems AS [P]
                  INNER JOIN [tblMakeUseType] AS [MUT] WITH(NOLOCK)
                  INNER JOIN [ItemInventory] AS [I] WITH(NOLOCK) ON [MUT].[MakeUseTypeID] = [I].[MakeUseTypeID] ON [P].[ItemID] = [I].[NCItemInventoryID]

正如你首先看到的 INNER JOIN没有 ON子句，但在第二个内部连接之后有 ON第一条 INNER JOIN ，我以前从未见过，有什么方法可以进行反向工程并用作tipcal INNER JOIN ?我的意思是每个人都带着他 ON条款？问候

Answer 1

您的查询被解释为:

FROM @POItems [P] INNER JOIN
     ([tblMakeUseType] [MUT] INNER JOIN
      [ItemInventory] [I] 
      ON [MUT].[MakeUseTypeID] = [I].[MakeUseTypeID]
     )
    ON [P].[ItemID] = [I].[NCItemInventoryID]

这可以。但是您可以更传统地将其写为:

FROM [tblMakeUseType] [MUT] INNER JOIN
     [ItemInventory] [I] 
     ON [MUT].[MakeUseTypeID] = [I].[MakeUseTypeID] INNER JOIN
     @POItems [P]
     ON [P].[ItemID] = [I].[NCItemInventoryID]

或者:

FROM @POItems [P] INNER JOIN
     [ItemInventory] [I] 
     ON [P].[ItemID] = [I].[NCItemInventoryID] INNER JOIN
     [tblMakeUseType] [MUT]
     ON [MUT].[MakeUseTypeID] = [I].[MakeUseTypeID] 

表的顺序对于内连接无关紧要，尽管必须在表的别名用于 ON 之前声明表。状况。