mysql - sql查询时如何动态更换连接表

Question

当type == 1时，course_id关联的时t_course_info 这张表

当type == 2时，course_id关联的是t_venue_course_info这张表

所以现在，我在查询的时候，如何才能根据type来判断关联哪张表呢？而且查询的时候会对关联表的数据进行筛选。

求大家帮忙！

Answer 1

mysql has a case when, please explore it yourself

Answer 2

select * from course c
left join t_course_info tci
on tci.id = c.course_id and c.type = 1
left join t_venue_course_info tvci
on tcvi.id = c.course_id and c.type = 2

Answer 3

Mybatis’ isEqual can implement this dynamic sql, but for these two businesses, wouldn’t it be better to just write two sql directly?