Oracle連線查詢

--交叉連線（會產生笛卡爾積）

select * from emp cross join dept;

--自然連線(可自動匹配關聯欄位並消除笛卡爾積)

select * from emp natural join dept;

--join...using,using子句後跟關聯的字段

select * from emp e join dept using(deptno);

--join...on,on子句後面跟關聯的條件

select * from emp e join salgrade s on (e.sal between s.losal and s.hisal);

--左外連線left outer join...on

select * from emp e left outer join dept d on (e.deptno = d.deptno);

--左外連線也可以寫成這樣：

select * from emp e ,dept d where e.deptno = d.deptno(+);

--右外連線right outer join...on

select * from emp e right outer join dept d on (e.deptno = d.deptno);

--右外連線也可以寫成這樣：

select * from emp e ,dept d where e.deptno(+) = d.deptno;

--全外連線full outer join

select * from emp e full outer join dept d on (e.deptno = d.deptno);

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