SQL强化

--举例：
select 
       a.sex,
       b.city,
       count(1) as cnt,
       sum(salary) as sum1
from table1 a
join table2 b on a.id=b.id
where a.name=b.name
group by a.sex,b.city
having cnt>=2
order by a.sex,b.city
limit 10
--或者是
select distinct
       a.sex,
       b.city,
       a.age
from table1 a
join table2 b on a.id=b.id
where a.name=b.name
order by a.sex,b.city
limit 10