create table a(
aid number,
aname varchar2(20)
);
create table b(
bid number,
bname varchar2(20)
);
create table c(
cid number,
cname varchar2(20)
);
insert into a(aid,aname)
SELECT 1,'a1' FROM dual
union all
SELECT 2,'a2' FROM dual;
insert into b
SELECT 1,'b1' FROM dual;
insert into c
SELECT 2,'c2' FROM dual
union all
SELECT 1,'c1' FROM dual;
commit;
1、SELECT * FROM a left join b on a.aid=b.bid left join c on c.cid= a.aid;
结果：
2、SELECT * FROM a left join b on a.aid=b.bid left join c on c.cid= b.bid;
3、SELECT * FROM a left join b on a.aid=b.bid right join c on c.cid= b.bid;
4、SELECT * FROM a inner join b on a.aid=b.bid right join c on c.cid= b.bid;
5、SELECT * FROM a inner join b on a.aid=b.bid left join c on c.cid= b.bid;
6、SELECT * FROM a cross join c
