通过多个联接删除行

Question

我正在尝试通过连接多个表来删除行，如您所见，但这会引发错误：

DELETE FROM Reg INNER JOIN
            RegDoc ON Reg.RegId = RegDoc.RegId INNER JOIN
            Doc ON RegDoc.DocId = Doc.DocId
WHERE Doc.Name LIKE N'%Title%'

出现错误：

消息156，级别15，状态1，第1行关键字'INNER'附近的语法错误。

Answer 1

正确的语法是

DELETE [ FROM ] { <object> } 
[ FROM <table_source>]
[ WHERE { <search_condition> } ]

应用于您的示例，这将成为

DELETE FROM Reg 
FROM  Reg
      INNER JOIN RegDoc ON Reg.RegId = RegDoc.RegId 
      INNER JOIN Doc ON RegDoc.DocId = Doc.DocId
WHERE Doc.Name LIKE N'%Title%'

注意表的两个引用Reg

可以通过别名进一步缩短（尽管在这种情况下几乎不需要）

DELETE FROM r
FROM  Reg r
      INNER JOIN RegDoc ON r.RegId = RegDoc.RegId 
      INNER JOIN Doc ON RegDoc.DocId = Doc.DocId
WHERE Doc.Name LIKE N'%Title%'

MSDN示例

DELETE FROM Sales.SalesPersonQuotaHistory 
FROM Sales.SalesPersonQuotaHistory AS spqh
INNER JOIN Sales.SalesPerson AS sp
ON spqh.BusinessEntityID = sp.BusinessEntityID
WHERE sp.SalesYTD > 2500000.00;