关于外联接: 你观察一下一下SQL的运行结果会有些感性认识create table tab1 (id char(10)); create table tab2 (id char(10));insert into tab1 values(1); insert into tab1 values(2); insert into tab1 values(3);insert into tab2 values(2); insert into tab2 values(3); insert into tab2 values(4); select id from tab1; select id from tab2;select tab1.id,tab2.id from tab1,tab2 where tab1.id=tab2.id; select tab1.id,tab2.id from tab1,tab2 where tab1.id(+)=tab2.id; select tab1.id,tab2.id from tab1,tab2 where tab1.id=tab2.id(+);
内联 select * from a,b where a.id=b.id 外联 select * from a,b where a.id=b.id(+)
you should see oracle sql reference http://gigabase.idi.ntnu.no/oradoc/nav/docindex.htm
你观察一下一下SQL的运行结果会有些感性认识create table tab1 (id char(10));
create table tab2 (id char(10));insert into tab1 values(1);
insert into tab1 values(2);
insert into tab1 values(3);insert into tab2 values(2);
insert into tab2 values(3);
insert into tab2 values(4);
select id from tab1;
select id from tab2;select tab1.id,tab2.id from tab1,tab2 where tab1.id=tab2.id;
select tab1.id,tab2.id from tab1,tab2 where tab1.id(+)=tab2.id;
select tab1.id,tab2.id from tab1,tab2 where tab1.id=tab2.id(+);
select * from a,b where a.id=b.id
外联
select * from a,b where a.id=b.id(+)
http://gigabase.idi.ntnu.no/oradoc/nav/docindex.htm