SubSelect和Join的T-SQL语句 - 不明确的列名错误

Question

我花了几个小时研究一个非常简单的T-SQL语句的答案.
情况就是这样.我想通过帮助台数据库进行报告.我有一个表(calllog),其中包含有关故障单的基本非重复信息和另一个事务表(Asgnmnt),其中包含对不同人员的各种分配以解决问题.我只是想确定Asgnmnt表中的最后一个分配,将它与呼叫日志文件链接,并使用外部选择中的数据来进行更多的数据报告.Asgnmnt表包含一个字段调用HEATSeq.给定CallID的最高HEATSeq将是最后一次分配.这是我的T-SQL语句和错误.

SELECT
Callid,
Priority,
RecvdDate,
RecvdTime,
ClosedDate,
ClosedTime,
CustID,
CallType,
CallDesc,
HeatSEQ#
FROM
      (Select 
      a.Callid, 
      a.Priority,
      a.RecvdDate,
      a.RecvdTime,
      a.ClosedDate,
      a.ClosedTime,
      a.CustID,
      a.CallType,
      a.CallDesc,
      (select TOP 1 HEATSeq from Asgnmnt f
      WHERE  a.CallID = f.CallID
      ORDER BY HEATSeq desc) as HeatSeq#
      FROM dbo.CallLog a 
      where a.CallID = '00520308') as z
LEFT OUTER JOIN dbo.Asgnmnt c on z.Callid=c.CallID and z.HeatSeq# = c.HEATSeq

这是[错误]

Msg 209, Level 16, State 1, Line 2
Ambiguous column name 'Callid'.
Msg 209, Level 16, State 1, Line 9
Ambiguous column name 'CallType'

Answer 1

您可能在z和c中都有Callid和CallType(至少).对于外部查询中的至少那些列,请使用表别名:

SELECT
z.Callid, -- No longer ambiguous
z.Priority,
z.RecvdDate,
z.RecvdTime,
z.ClosedDate,
z.ClosedTime,
z.CustID,
z.CallType,
z.CallDesc,
z.HeatSEQ#
FROM
      (Select 
      a.Callid, 
      a.Priority,
      a.RecvdDate,
      a.RecvdTime,
      a.ClosedDate,
      a.ClosedTime,
      a.CustID,
      a.CallType,
      a.CallDesc,
      (select TOP 1 HEATSeq from Asgnmnt f
      WHERE  a.CallID = f.CallID
      ORDER BY HEATSeq desc) as HeatSeq#
      FROM dbo.CallLog a 
      where a.CallID = '00520308') as z
LEFT OUTER JOIN dbo.Asgnmnt c on z.Callid=c.CallID and z.HeatSeq# = c.HEATSeq