--展现oracle数据库表间各种连接
--测试表
SQL> select * from test1;

        ID NAME
---------- --------------------
         1 yallonking
         2 yallonking
         3 yallonking
         4 yallonking

SQL> select * from test2;

        ID NAME
---------- --------------------
         4 oraking
         3 oraking
         5 oraking
         6 oraking
--左连接
SQL> select a.*,b.* from test1 a,test2 b where a.id=b.id(+);

        ID NAME                         ID NAME
---------- -------------------- ---------- --------------------
         4 yallonking                    4 oraking
         3 yallonking                    3 oraking
         1 yallonking
         2 yallonking
        
SQL> select a.*,b.* from test1 a left join test2 b on a.id=b.id;

        ID NAME                         ID NAME
---------- -------------------- ---------- --------------------
         4 yallonking                    4 oraking
         3 yallonking                    3 oraking
         1 yallonking
         2 yallonking

--右连接
SQL> select a.*,b.* from test1 a,test2 b where a.id(+)=b.id;

        ID NAME                         ID NAME
---------- -------------------- ---------- --------------------
         3 yallonking                    3 oraking
         4 yallonking                    4 oraking
                                         6 oraking
                                         5 oraking
                                         
SQL> select a.*,b.* from test1 a right join test2 b on a.id=b.id;

        ID NAME                         ID NAME
---------- -------------------- ---------- --------------------
         3 yallonking                    3 oraking
         4 yallonking                    4 oraking
                                         6 oraking
                                         5 oraking
                                         
--等值连接
SQL> select a.*,b.* from test1 a,test2 b where a.id=b.id;

        ID NAME                         ID NAME
---------- -------------------- ---------- --------------------
         4 yallonking                    4 oraking
         3 yallonking                    3 oraking
         
SQL> select a.*,b.* from test1 a join test2 b on a.id=b.id;

        ID NAME                         ID NAME
---------- -------------------- ---------- --------------------
         4 yallonking                    4 oraking
         3 yallonking                    3 oraking
         
--笛卡尔积连接
SQL> select a.*,b.* from test1 a,test2 b;

        ID NAME                         ID NAME
---------- -------------------- ---------- --------------------
         1 yallonking                    4 oraking
         1 yallonking                    3 oraking
         1 yallonking                    5 oraking
         1 yallonking                    6 oraking
         2 yallonking                    4 oraking
         2 yallonking                    3 oraking
         2 yallonking                    5 oraking
         2 yallonking                    6 oraking
         3 yallonking                    4 oraking
         3 yallonking                    3 oraking
         3 yallonking                    5 oraking

        ID NAME                         ID NAME
---------- -------------------- ---------- --------------------
         3 yallonking                    6 oraking
         4 yallonking                    4 oraking
         4 yallonking                    3 oraking
         4 yallonking                    5 oraking
         4 yallonking                    6 oraking

16 rows selected.

SQL> select a.*,b.* from test1 a join test2 b on 1=1;

        ID NAME                         ID NAME
---------- -------------------- ---------- --------------------
         1 yallonking                    4 oraking
         1 yallonking                    3 oraking
         1 yallonking                    5 oraking
         1 yallonking                    6 oraking
         2 yallonking                    4 oraking
         2 yallonking                    3 oraking
         2 yallonking                    5 oraking
         2 yallonking                    6 oraking
         3 yallonking                    4 oraking
         3 yallonking                    3 oraking
         3 yallonking                    5 oraking

        ID NAME                         ID NAME
---------- -------------------- ---------- --------------------
         3 yallonking                    6 oraking
         4 yallonking                    4 oraking
         4 yallonking                    3 oraking
         4 yallonking                    5 oraking
         4 yallonking                    6 oraking

16 rows selected.