SQL：计入左连接问题

Question

这打印出我期望的结果，但我不知道如何计算其中有多少行

select distinct(post.city), zips.zip_code, zips.population, post.stabbr
from zips left join
     post
     on zips.zip_code=post.zip
where post.stabbr like 'MO' and zips.population > 5000 and
      post.longitud > (select avg (zips.lon) from zips where state_prefix like 'mo' )
group by post.city;

我以为

select count(*)
from zips left join
     post
     on zips.zip_code=post.zip
where post.stabbr like 'MO' and zips.population > 5000 and
      post.longitud > (select avg (zips.lon) from zips where state_prefix like 'mo' )
group by post.city;

会工作，但它打印了所有 41 行，我相信城市的 grouped by。

对我有什么想法吗？

Answer 1

我想你想要 count(distinct) 而没有 group by:

select count(distinct post.city)
from zips left join
     post
     on zips.zip_code=post.zip
where post.stabbr like 'MO' and zips.population > 5000 and
      post.longitud > (select avg(zips.lon) from zips where state_prefix like 'mo' );