inner join和outer join
inner join指表格交集
outer join分为left join, right join, full outer join
select * from A,B where A.id=B.id; 和inner join效果一样。
select * from A left join B on A.id=B.id; A中数据都包括,B中没有的以null代替。
2022-07-09 17:21:19
inner join和outer join
inner join指表格交集
outer join分为left join, right join, full outer join
select * from A,B where A.id=B.id; 和inner join效果一样。
select * from A left join B on A.id=B.id; A中数据都包括,B中没有的以null代替。