select 查询和具有结果的相同查询

Question

我遇到了一些 "complicated" 查询，例如：

with q1 as (
select w.entity_id, p.actionable_group, p.error_type
 from issue_analysis p
 join log l on p.id = l.issue_analysis_id
 join website w on l.website_id = w.id
 where l.date >= '2016-06-01'
 group by 1, 2, 3
),
q2 as (
select w.entity_id, p.actionable_group, p.error_type
 from issue_analysis p
 join log l on p.id = l.issue_analysis_id
 join website w on l.website_id = w.id
 where l.date >= '2016-06-01'
 group by 1, 2, 3
 having count(1) = 1
)

并尝试

SELECT q1.entity_id, count(q1.entity_id), count(q2.entity_id)
from q1, q2
group by 1
order by 1

但结果为我提供了一个 "wrong" 数据，因为它并没有真正包含这两个计数...

您能否描述无需大量嵌套查询即可解决此类问题的最 "cleaner" 方法？

如果它可能有帮助 - q2 类似于 q1 但在末尾有 having count(1) = 1。

P.S。 文档link答案很简单就可以了。

Answer 1

毫无疑问，您得到的是笛卡尔积，这会影响聚合。相反，聚合 before 进行连接：

select q1.entity_id, q1_cnt, q2_cnt
from (select q1.entity_id, count(*) as q1_cnt
      from q1
      group by q1.entity_id
     ) q1 join
     (select q2.entity_id, count(*) as q2_cnt
      from q2
      group by q2.entity_id
     ) q2
     on q1.entity_id = q2.entity_id;

select 查询和具有结果的相同查询

select query and same query with having results

sql

postgresql

postgresql-9.3