Question

请参阅下面我正在努力的代码：

select * 
from AAA_PROD_XEUSS.P_E_LVR_CQT CQT 
left join AAA_PROD_XEUSS.P_F_OPERATION OPER
on CQT.OPERATION = OPER.OPERATION
union
select * 
from BBB_PROD_XEUSS.P_E_LVR_CQT CQT
left join BBB_PROD_XEUSS.P_F_OPERATION OPER
on CQT.OPERATION = OPER.OPERATION
where CQT.PROCESS = '1111'
Order by OPERATION

我收到以下错误：错误[42877] [IBM] [DB2 / LINUXX8664] SQL0197N ORDER BY子句中不允许使用限定列名。任何提出错误的建议解决方案

谢谢

Answer 1

在外面使用order by子句，并为内部部分的选择列表中的所有列添加别名。

（ cqt.operation或oper.operation中的一个可能在内部首选，因为它们匹配为相等）：

Select * 
from
    (select cqt.col1, cqt.col2, oper.* 
     -- where "operation" column is exempted from cqt list, 
     --  since the table aliased as oper already has "operation" column.
     from AAA_PROD_XEUSS.P_E_LVR_CQT CQT 
     left join AAA_PROD_XEUSS.P_F_OPERATION OPER on CQT.OPERATION = OPER.OPERATION
     union
     select cqt.col1, cqt.col2, oper.*
     from BBB_PROD_XEUSS.P_E_LVR_CQT CQT
     left join BBB_PROD_XEUSS.P_F_OPERATION OPER on CQT.OPERATION = OPER.OPERATION
     where CQT.PROCESS = '1111'
) 
Order by OPERATION

Answer 2

您可以使用order by，但需要明确列出列。无论如何，这是一个很好的做法：

select cqt.*, oper.?, oper.?, . . .
from AAA_PROD_XEUSS.P_E_LVR_CQT CQT left join
     AAA_PROD_XEUSS.P_F_OPERATION OPER
    on CQT.OPERATION = OPER.OPERATION
union
select cqt.*, oper.?, oper.?, . . .
from BBB_PROD_XEUSS.P_E_LVR_CQT CQT left join
     BBB_PROD_XEUSS.P_F_OPERATION OPER
     on CQT.OPERATION = OPER.OPERATION
where CQT.PROCESS = '1111'
Order by OPERATION;

OPERATION列应来自CQT表。 ?是OPER中其他列的占位符。这假设两个CQT表具有相同的列，并且具有以相同顺序定义的相同类型。更好的做法是列出所有列。

Answer 3

如果您使用的是Db2 11.1，则可以使用JOIN USING语法来避免在结果集https://www.ibm.com/support/knowledgecenter/en/SSEPGG_11.1.0/com.ibm.db2.luw.sql.ref.doc/doc/r0059207.html

中包含两个已连接列的副本

E.g。这些表格

create table AAA_PROD_XEUSS.P_E_LVR_CQT   (i int, OPERATION int, PROCESS char(4)););
create table AAA_PROD_XEUSS.P_F_OPERATION (b int, OPERATION int);
create table BBB_PROD_XEUSS.P_E_LVR_CQT   (c int, OPERATION int, PROCESS char(4));
create table BBB_PROD_XEUSS.P_F_OPERATION (b int, OPERATION int);

此选择

select * 
from AAA_PROD_XEUSS.P_E_LVR_CQT CQT 
left join AAA_PROD_XEUSS.P_F_OPERATION OPER
USING ( OPERATION )
union
select * 
from BBB_PROD_XEUSS.P_E_LVR_CQT CQT
left join BBB_PROD_XEUSS.P_F_OPERATION OPER
USING ( OPERATION )
where CQT.PROCESS = '1111'
Order by OPERATION

只返回一个名为OPERATION的列

OPERATION I PROCESS B
--------- - ------- -

0 record(s) selected.

P.S。您可能更愿意使用UNION ALL而不仅仅是UNION来避免Db2必须对所有行进行排序以删除重复项

SQL在Union语句中使用Order By

3 个答案: