mysql count 多表联查问题

a right join d right join c====(a right join d) right join c

你的目的是找c表中能在a表找到对应值记录的数量找d表中能在a表找到对应值记录的数量

但是你最后一句的涵义是a表中能在d表和c表同时找到对应值的数量，此时count(c.p_rel_id)其实是你c表的数量，就是那个504的涵义，至于count(d.p_rel_id)为什么等于504 完全是凑巧~~~

select sum(cnt) from

(

select count(*) as cnt from tb_one where title like '%蜡笔小新%'

union all

select count(*) as cnt from tb_two where title like '%蜡笔小新%'

union all

select count(*) as cnt from tb_three where title like '%蜡笔小新%') t

这样不就可以么？

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