自定义列上的 Where 子句

Question

select c.base_id,case when c.type is not null then c.type else g.type end as type, c.function_id
from cust c 
left join category cg on c.cat_id=cg.id
where c.type='privelleged'; --- where clause is not working as expected

上面的 query.The where 子句没有按预期工作，我漏掉了什么。我需要在派生的 'type' 列上应用 where 子句。我如何在 Oracle 中实现它。

提前致谢

Answer 1

我怀疑您只想 coalesce() -- 在 select 和 where 中：

select c.base_id, coalesce(c.type, g.type) as type, c.function_id
from cust c left join
     category cg
     on c.cat_id = cg.id
where coalesce(c.type, g.type) = 'privileged';

Answer 2

您不能按照您想要的方式使用 derived 列 - 您还需要在 WHERE 中使用相同的 CASE：

select c.base_id,
  case when c.type is not null then c.type 
       else g.type 
  end as type, 
  c.function_id
from cust c 
left join category cg on c.cat_id = cg.id
where case when c.type is not null then c.type     --> here
           else g.type 
      end = 'privelleged';

或者，将当前查询用作 CTE（或子查询）并对其应用过滤器：

with temp as
  (select c.base_id,
          case when c.type is not null then c.type 
               else g.type 
          end as type, 
          c.function_id
   from cust c 
   left join category cg on c.cat_id = cg.id
  )
select *
from temp
where type = 'privelleged';

自定义列上的 Where 子句

Where clause on custom column

sql

database

oracle

oracle11g