连接的一种,看看这个,做一遍,看看结果,也许有点启发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(+);
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(+);
ID ID
---------- ----------
2 2
3 3
4
第三个为
ID ID
---------- ----------
1
2 2
3 3意思是不是没有(+)的连接可以为有(+)那边没有的数据