Question

这是我的初步查询：

select 
CASE WHEN a.TO_WG_ID is null 
and a.CREATED_DATE_TIME = 
(select min(b.created_date_time) from ymtn.message b 
where b.thread_id = a.thread_id) THEN 1 ELSE 0
END AS "Created"
from ymtn.MESSAGE a 
left join YMTN.WORKGROUP b
ON a.FROM_WG_ID=b.WORKGROUP_ID
where b.WORKGROUP_ID='1STOP_PROCESS'

它给了我一列一堆1＆＃39;和0＆＃39; s。我想要的只是总和..只是一个数字，例如如果我在case语句前面放了一个SUM，我会收到这个错误： 消息130，级别15，状态1，行5 无法对包含聚合或子查询的表达式执行聚合函数。那么我该怎么做？我使用了这个查询：

select count(CREATED_DATE_TIME) as 'Created'
from ymtn.MESSAGE a
LEFT JOIN YMTN.WORKGROUP b
ON a.FROM_WG_ID=b.WORKGROUP_ID
where CREATED_DATE_TIME=(SELECT MIN(b.CREATED_DATE_TIME) FROM YMTN.MESSAGE b WHERE
 b.THREAD_ID = a.THREAD_ID)
and a.TO_WG_ID is null
and b.WORKGROUP_ID='1STOP_PROCESS'

但是我希望它在case语句中工作，而不必将嵌套的select向下移动到WHERE子句。

Answer 1

你可以将整个事物扔进子查询并总结一下吗？

select sum(Created)
from (
    select 
    CASE WHEN a.TO_WG_ID is null 
    and a.CREATED_DATE_TIME = 
    (select min(b.created_date_time) from ymtn.message b 
    where b.thread_id = a.thread_id) THEN 1 ELSE 0
    END AS "Created"
    from ymtn.MESSAGE a 
    left join YMTN.WORKGROUP b
    ON a.FROM_WG_ID=b.WORKGROUP_ID
    where b.WORKGROUP_ID='1STOP_PROCESS'
) a

如何SUM包含嵌套select语句的case语句？

1 个答案: