mysql - #1054 - 'on 子句'中的未知列 'e.ProjectID'

Question

我收到错误 #1054 - 'on 子句' 中的未知列 'e.ProjectID' 使用以下 SQL

SELECT ProjectID
FROM Project as p
INNER JOIN (SELECT EquipID , EquipName , EquipTypeID , (EquipPrice*Quantity) As CstAmount     FROM Equipment) as e
ON p.ProjectID=e.ProjectID

Answer 1

您的子查询没有将该列暴露给外部查询。

SELECT ProjectID
FROM   Project As p
 INNER
  JOIN (
        SELECT ProjectID
             , EquipID
             , EquipName
             , EquipTypeID
             , (EquipPrice*Quantity) As CstAmount
        FROM   Equipment
       ) As e
    ON p.ProjectID = e.ProjectID

但是，如果您只想返回 ProjectID，那么我建议您改为执行此查询：

SELECT ProjectID
FROM   Project
WHERE  EXISTS (
         SELECT *
         FROM   Equipment
         WHERE  ProjectID = Project.ProjectID
       )

Answer 2

您不需要任何子查询。只需将项目表与设备表连接起来，如下所示

SELECT p.ProjectID,e.EquipID ,e.EquipName ,e.EquipTypeID ,e.EquipPrice* e.Quantity as CstAmount from Project P join Equipment e on  p.ProjectID=e.ProjectID

Answer 3

你可以在没有子查询的情况下做到这一点

 SELECT p.ProjectID ,e.EquipID , e.EquipName , e.EquipTypeID , (e.EquipPrice * e.Quantity) As CstAmount
 FROM Project as p
 INNER JOIN Equipment  as e
 ON p.ProjectID= e.ProjectID

Answer 4

你想做什么？您的查询可以重写如下，但我怀疑这是您想要的

SELECT p.ProjectID
FROM Project as p
INNER JOIN Equipment as e
ON p.ProjectID = e.ProjectID

您是否还需要选择子查询的字段？