sql - oracle中的group by和union

Question

我想联合 2 个查询，但在 oracle 中遇到错误。

select count(*) as faultCount,
       COMP_IDENTIFIER 
from CORDYS_NCB_LOG 
where AUDIT_CONTEXT='FAULT' 
union 
select count(*) as responseCount,
       COMP_IDENTIFIER 
from CORDYS_NCB_LOG 
where AUDIT_CONTEXT='RESPONSE' 
group by COMP_IDENTIFIER  
order by responseCount; 

两个查询单独运行完美。但是当使用联合时，它说 ORA-00904: "RESPONSECOUNT": invalid identifier

Answer 1

你遇到的错误

在 Oracle 中，最好始终为每个 UNION 中的每个列命名。子查询方式相同。在您的情况下，以下应该有效:

select count(*) as theCount,
       COMP_IDENTIFIER 
from CORDYS_NCB_LOG 
where AUDIT_CONTEXT='FAULT' 
group by COMP_IDENTIFIER -- don't forget this
union 
select count(*) as theCount,
       COMP_IDENTIFIER 
from CORDYS_NCB_LOG 
where AUDIT_CONTEXT='RESPONSE' 
group by COMP_IDENTIFIER  
order by theCount; 

也可以看看:

Curious issue with Oracle UNION and ORDER BY

当然，一个好的解决方法是使用 a_horse_with_no_name 建议的索引列引用。

您真正想要的查询

但是，根据您的评论，我怀疑您想编写一个完全不同的查询，即:

select count(case AUDIT_CONTEXT when 'FAULT'    then 1 end) as faultCount,
       count(case AUDIT_CONTEXT when 'RESPONSE' then 1 end) as responseCount,
       COMP_IDENTIFIER 
from CORDYS_NCB_LOG 
where AUDIT_CONTEXT in ('FAULT', 'RESPONSE')
group by COMP_IDENTIFIER  
order by responseCount;