SQL Server 错误 列名不明确

Question

无法理解这个 SQL 查询出了什么问题：

USE [My_db]
GO

SELECT ItemId
      ,Subject
      ,CreatedOn
  FROM ItemBase AS e
      INNER JOIN ItemExtensionBase AS p
      ON e.ItemId = p.ItemId
GO

错误：

 Msg 209, Level 16, State 1, Line 4
 Ambiguous column name 'ItemId'.

ItemId两个表中都存在列。

Answer 1

USE [My_db]
GO

SELECT e.ItemId
      ,Subject
      ,CreatedOn
  FROM ItemBase AS e
      INNER JOIN ItemExtensionBase AS p
      ON e.ItemId = p.ItemId
GO

您需要告诉它从哪个表中获取 itemid 字段