Question

我有这个查询，它根据定义的时间间隔选择每个“消息代码”的计数。

expect()

条目输出

SELECT coalesce(count(case when messagecode = 'F-100' then 'F-100' end), 0) as fixed,
       coalesce(count(case when messagecode = 'H-100' then 'H-100' end), 0) as hope,
       coalesce(count(case when messagecode = 'G-100' then 'G-100' end), 0) as good, 
       coalesce(count(case when messagecode = 'T-100' then 'T-100' end), 0) as todo
       FROM messages WHERE messagetime >= current_timestamp - ('5' * interval '1 minute')

我想做类似的事情但是要选择具有此消息代码的唯一ID的数量，我知道我应该从做什么开始

fixed: 115,
hope: 334,
good: 1045,
todo: 6000

但我的问题是，我还不知道如何在同一查询的多个条件下执行此操作。预期产出：

SELECT coalesce(count(DISTINCT id), 0) ...

我将如何实现它？

Answer 1

查询可能如下所示：

SELECT coalesce(count(distinct case when messagecode = 'F-100' then id end), 0) as fixed,
       coalesce(count(distinct case when messagecode = 'H-100' then id end), 0) as hope,
       coalesce(count(distinct case when messagecode = 'G-100' then id end), 0) as good, 
       coalesce(count(distinct case when messagecode = 'T-100' then id end), 0) as todo
       FROM messages WHERE messagetime >= current_timestamp - ('5' * interval '1 minute')

根据多个条件构建postgresql查询

1 个答案: