如果您认为返回的结果不同，那么应该使用“union all”，因为您只使用“union”，sql会对结果进行区分，从而影响查询的性能

很容易：）这应该适用于最常见的db引擎：

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

正如edamame所说的，你可能需要阅读每个团队的两个结果。这个问题本身并不清楚，但可以这样解决：

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