【sql】之使用sql根据身份证查询过生日人数

 根据当前日期查询有多少人过生日

select * from people p where substr(p.idcard,11,2) = DATE_FORMAT(NOW(),'%m');

查询price一样的人数

select * from people  where price in (select price  from people group by price having count(*)>1);

 上面这段sql的性能有很大的局限性

select price  from people group by price having count(*)>1

上面这段代码的意思是以price为一组，结果大于1的price