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table1,table2并且table3有不同的列，但都有一个OrderDate列。我想从所有 3 个表中获取一组行的结果，并且我希望最终结果集按OrderDate.

( select * from table1 LEFT  join table2 on 0=1 LEFT  join table3 on 0=1
     where somedate <= table1.orderdate ) 

union all

( select * from table1 RIGHT join table2 on 0=1 LEFT  join table3 on 0=1   
     where somedate <= table2.orderdate ) 

union all

( select * from table1 RIGHT join table2 on 0=1 RIGHT join table3 on 0=1
    where somedate <= table3.orderdate )

这可行，但我希望这个结果集按 排序orderdate，所以我添加：

order by case when table1.orderdate is not null then table1.orderdate
              when table2.orderdate is not null then table2.orderdate
              else table3.orderdate end

SQL Server 返回错误“如果语句包含 UNION、INTERSECT 或 EXCEPT 运算符，则 ORDER BY 项必须出现在选择列表中。”

如果我更换

select *

经过

select *, table1.orderdate, table2.orderdate, table3.orderdate

我犯了同样的错误。

嗯？谢谢。

4

2 回答 2

1

试试这个

Select * from 
(( select * from table1 LEFT  join table2 on 0=1 LEFT  join table3
     where somedate <= table1.orderdate ) 

union all

( select * from table1 RIGHT join table2 on 0=1 LEFT  join table3    
     where somedate <= table2.orderdate ) 

union all

( select * from table1 RIGHT join table2 on 0=1 RIGHT join table3
    where somedate <= table3.orderdate )) A

Order by A.orderdate
于 2012-05-20T05:03:33.310 回答
0

我使用公用表表达式解决了这个问题，这就是我所做的：

WITH JoinedTable as
(
    ( select table1.col1 as t1col1, table2.col2 as t1col2 [etc...] 
      from table1 LEFT  join table2 on 0=1 LEFT  join table3 on 0=1
      where somedate <= table1.orderdate ) 

    union all

    ( select table1.col1 as t1col1, table2.col2 as t1col2 [etc...] 
      from table1 RIGHT join table2 on 0=1 LEFT  join table3 on 0=1   
      where somedate <= table2.orderdate ) 

    union all

    ( select table1.col1 as t1col1, table2.col2 as t1col2 [etc...] 
      from table1 RIGHT join table2 on 0=1 RIGHT join table3 on 0=1
      where somedate <= table3.orderdate )
)

select *, case when t1orderdate is not null then t1orderdate
               when t2orderdate is not null then t2orderdate
               else t3orderdate end
               AS DateForOrderingResultSet
from JoinedTable order by DateForOrderingResultSet

这

table1.col1 as t1col1, table2.col2 as t1col2 [etc...]

如果, ,具有相同的列名（例如），*则无法避免替换，否则 SQL Server 会抛出一个错误，说是模棱两可的：它无法知道这是否意味着or或。table1table2table3IDJoinedTable.IDtable1.IDtable2.IDtable3.ID

于 2012-05-20T20:16:37.397 回答