这两天看到一张 sql join 图, 感觉非常直观. 在这里分享下
按照图片竖着的顺序写下每种 sql
- a left join b on a.key = b.key
- a left join b on a.key = b.key where b.key is null
- a full outer join b on a.key = b.key
- a. inner join b on a.key = b.key
- a full outer join b on a.key = b.key where a.key is null or b.key is null
- a right join b on a.key = b.key
- a right join b on a.key = b.key where a.key is null
