删除 select 语句中存在 column 的行

Posted 2023-03-28

【中文标题】删除 select 语句中存在 column 的行

【英文标题】：Remove rows where column exists in select statement

【发布时间】：2018-10-19 23:20:21

【问题描述】：

我想删除 select 语句中存在特定列的行，例如：

delete from [ProjectCustomer] pcc 
where ProjectKey in (
  select p.ProjectKey  
  FROM [Project] AS [p] inner JOIN [ProjectDesign] AS [pd] ON [p].[ProjectKey] = [pd].[ProjectKey]
  inner JOIN [Design] AS [d] ON [pd].[DesignKey] = [d].[DesignKey]
  inner JOIN [ProjectCustomer] AS [pc] ON [pc].[ProjectKey] = [p].[ProjectKey]
  inner join Customer as c on pc.CustomerKey = c.CustomerKey
  where d.Folio = 3014)

但是在 delete 语句的 where 子句中我得到了

where 子句附近的语法不正确

我做错了什么？问候

【问题讨论】：

您能否为上述查询添加足够的数据库架构以引用现有的表和列名？它可能会帮助我诊断您的问题。

应该是delete pcc from [ProjectCustomer] pcc

尝试删除 pcc 别名，因为您不使用它。

【参考方案1】：

具有表别名的 DELETE 语句具有不同的语法，因此您可以删除未使用的别名或更改删除语句，如 @Martin 评论。

delete pcc from [ProjectCustomer] pcc

我会准备使用INNER JOIN 而不是IN 来修改查询

delete pcc from [ProjectCustomer] AS pcc 
  inner join [Project] AS [p] ON [p].ProjectKey = [pcc].ProjectKey
  inner JOIN [ProjectDesign] AS [pd] ON [p].[ProjectKey] = [pd].[ProjectKey]
  inner JOIN [Design] AS [d] ON [pd].[DesignKey] = [d].[DesignKey]
  inner JOIN [ProjectCustomer] AS [pc] ON [pc].[ProjectKey] = [p].[ProjectKey]
  inner join Customer as c on pc.CustomerKey = c.CustomerKey
  where d.Folio = 3014)

【参考方案2】：

我认为错误信息是

“pcc”附近的语法不正确

而不是

where 子句附近的语法不正确

您将收到第一条错误消息，因为您使用了错误的别名，所以当您没有加入目标表时，您可能需要

delete from [ProjectCustomer]
where ProjectKey in (
  select p.ProjectKey  
  FROM [Project] AS [p] inner JOIN [ProjectDesign] AS [pd] ON [p].[ProjectKey] = [pd].[ProjectKey]
  inner JOIN [Design] AS [d] ON [pd].[DesignKey] = [d].[DesignKey]
  inner JOIN [ProjectCustomer] AS [pc] ON [pc].[ProjectKey] = [p].[ProjectKey]
  inner join Customer as c on pc.CustomerKey = c.CustomerKey
  where d.Folio = 3014);

或者即使你仍然想使用别名

delete pcc from [ProjectCustomer] pcc
where pcc.ProjectKey in ...

【参考方案3】：

您可能可以稍微简化您的查询。我认为您不需要子查询，您可以在第一个 FROM 子句中指定要从中删除的表（没有别名），然后在第二个中加入表（根据需要使用别名）：

DELETE FROM ProjectCustomer
FROM ProjectCustomer pc
  INNER JOIN ProjectDesign pd ON pc.ProjectKey = pd.ProjectKey
    INNER JOIN Design d ON pd.DesignKey = d.DesignKey
WHERE d.Folio = 3014;

Customers 和 Products 表不应该是必需的，只要您设置了参照完整性并且 pc.CustomerKey 不可为空。