SQL /帕拉：合并多个查询（用不同的WHERE子句中）到一个

Question

我有以下查询：

'select team, count(distinct id) as distinct_id_count_w1 from myTable where timestamp > t1 and timestamp < t2 group by team' 

'select team, count(distinct id) as distinct_id_count_w2 from myTable where timestamp > t2 and timestamp < t3 group by team' 

是否有可能这两个查询合并成一个？谢谢！

Answer 1

轻松:)这应该上最常见的数据库引擎的工作原理：

select team, count(distinct id) as distinct_id_count_w1, null as distinct_id_count_w2 from myTable where timestamp > t1 and timestamp < t2 group by team 

UNION ALL 

select team, null as distinct_id_count_w1, count(distinct id) as distinct_id_count_w2 from myTable where timestamp > t2 and timestamp < t3 group by team 

如毛豆说，你可能需要阅读每队两个结果。这是不是从问题本身清楚，但可以用此方式解决：

SELECT 
    COALESCE(interval1.team interval2.team) AS team, 
    interval1.distinct_id_count_w1, 
    interval2.distinct_id_count_w2 
FROM (
    select team, count(distinct id) as distinct_id_count_w1 from myTable where timestamp > t1 and timestamp < t2 group by team 
) AS interval1 
FULL OUTER JOIN 
(
    select team, count(distinct id) as distinct_id_count_w2 from myTable where timestamp > t2 and timestamp < t3 group by team 
) AS interval2 
ON interval1.team IS NULL OR interval2.team IS NULL OR interval1.team = interval2.team 

Answer 2

如果u认为，返回的结果是不同的，U应使用“UNION ALL”，因为ü只能用“联盟”的工作，SQL将区分结果以影响查询