目录
场景1:left join + on a.xx = b.xx and a.xx2 = 'aa'
场景2:left join + on a.xx = b.xx and b.xx2 = 'aa'
场景3:left join + on a.xx = b.xx where b.xx2 = 'aa'
场景4:inner join + on a.xx = b.xx where a.xx2 = 'aa'
场景5:inner join + on a.xx = b.xx and a.xx2 = 'aa'
场景6:inner join + on a.xx = b.xx and b.xx2 = 'aa'
总结
场景1:left join + on a.xx = b.xx and a.xx2 = 'aa'
场景2:left join + on a.xx = b.xx and b.xx2 = 'aa'
场景3:left join + on a.xx = b.xx where b.xx2 = 'aa'
场景4:inner join + on a.xx = b.xx where a.xx2 = 'aa'
场景5:inner join + on a.xx = b.xx and a.xx2 = 'aa'
场景6:inner join + on a.xx = b.xx and b.xx2 = 'aa'
总结
1、where 条件可以理解为,关联后,数据作为一个整体的过滤条件
2、on 后面的and 条件为关联条件,如果是left join,则不对主表记录行数产生影响;如果是inner join则,效果等同于where条件