错误“where 子句中的未知列” - 出了什么问题？

Question

我使用的是 MySQL Server 5.7，我有这个查询：

select 
    regDate,
    userID,
    t.teamID,
    login
from
    tbl_user u
inner join 
    tbl_team t on u.userID = t.userID
where
    regDate >= DATE_ADD(CURDATE(), INTERVAL -2 MONTH)
    AND 
    (
        select sum(transactions) from (
            SELECT count(*) as transactions FROM tbl_pp where (fromTeamID = t.teamID or forTeamID = t.teamID) and transactionDate >= u.regDate
            union all
            SELECT count(*) as transactions FROM tbl_psc where (fromTeamID = t.teamID or toTeamID = t.teamID) and transactionDate >= u.regDate
            union all
            SELECT count(*) as transactions FROM tbl_mp where (fromTeamID = t.teamID or forTeamID = t.teamID) and transactionDate >= u.regDate
        ) as all
    ) > 0

我收到此错误：

错误代码：1054。“where 子句”中的未知列“t.teamID”

我确定这只是一个小问题，但我现在无法解决。并且teamID 列存在于表tbl_team 中。有人给我提示吗？

Answer 1

您不能将相关引用嵌套在一个以上的查询深处。你最好还是使用exists：

select u.regDate, u.userID, t.teamID, u.login
from tbl_user u inner join 
     tbl_team t
     on u.userID = t.userID
where u.regDate >= DATE_ADD(CURDATE(), INTERVAL -2 MONTH) and
      (exists (select 1
               from tbl_pp p
               where t.teamID in (p.fromTeamID, p.forTeamID) and
                     p.transactionDate >= u.regDate
              ) or
       exists (select 1
               from tbl_psc p
               where t.teamID in (p.fromTeamID, p.toTeamID) and
                     p.transactionDate >= u.regDate
              ) or
       exists (select 1
               from tbl_mp p
               where t.teamID in (p.fromTeamID, p.forTeamID) and
                     p.transactionDate >= u.regDate
              )
     )