mysql多表查询 查询排序

有 ask 问题表  和 answer回答表  回答表中的ask_id和 ask表中的id对应

1、查询

/*
查询回答了的
 */
select a.id,a.title,count(b.ask_id) as num from phome_ecms_ask a,phome_ecms_answer b where a.id=b.ask_id group by a.id  order by num desc

2、将ask问题表中的问题 按回答数量排序

/*
查询所有的问题 按回答数排序
 */
select a.id,a.title,count(b.ask_id) as num from phome_ecms_ask a left join phome_ecms_answer b on a.id=b.ask_id group by a.id  order by num desc