select country, count(organization) as N
from ismember
group by country
having N > 50;
select * from (
select country, count(organization) as N
from ismember
group by country) x
where N > 50;
每个HAVING
子句是否都可以像这样替换为子查询和WHERE
子句?还是有些情况下,HAVING
子句是绝对必要/更强大/更高效/更优等的?