Mysql使用union all统计多张表组合总数，并分别统计各表数量

select count(distinct(vehicleId)) as ‘总数’,
count(distinct(case when flag = ‘t2’ then vehicleId end)) as ‘表2数量’
from
(
SELECT ‘t1’ as flag, cf.vehicle_id as vehicleId FROM ota_campaign_feedback cf WHERE cf.campaign_id = 1021612 GROUP BY cf.vehicle_id
union all
SELECT ‘t2’ as flag, c.vehicle_id as vehicleId FROM ota_vehicle_upgrade_check c WHERE c.campaign_id = 1021612 GROUP BY c.vehicle_id
) tt

利用count(case when …)条件统计，结合临时flag变量实现。