oracle交集,并集,差集

引自：http://www.2cto.com/database/201308/238777.html

[sql] 
create table test1  
(  
 name varchar(10),  
 NN varchar(10)  
);  
insert into test1 values('test','A');  
insert into test1 values('test1','B');  
insert into test1 values('test1','C');  
insert into test1 values('test1','D');  
insert into test1 values('test1','E');  
create table test2  
(  
 name varchar(10),  
 NN varchar(10)  
);  
insert into test2 values('test','A');  
insert into test2 values('test2','B');  
insert into test2 values('test2','C');  
insert into test2 values('test2','D');  
insert into test2 values('test2','E');  
 
1、交集：intersect
[sql] 
SQL> select * from test1 intersect select * from test2;  
   
NAME       NN  
---------- ----------  
test       A  
 
2、并集：union、union all （注意两者的区别）
[sql] 
SQL> select * from test1 union select * from test2;  
   
NAME       NN  
---------- ----------  
test       A  
test1      B  
test1      C  
test1      D  
test1      E  
test2      B  
test2      C  
test2      D  
test2      E  
   
9 rows selected.  
[sql] 
SQL> select * from test1 union all select * from test2;  
   
NAME       NN  
---------- ----------  
test       A  
test1      B  
test1      C  
test1      D  
test1      E  
test       A  
test2      B  
test2      C  
test2      D  
test2      E  
   
10 rows selected.  
 
3、差集：minus
[sql] 
SQL> select * from test1 minus select * from test2;  
   
NAME       NN  
---------- ----------  
test1      B  
test1      C  
test1      D  
test1      E  
   
SQL> select * from test2 minus select * from test1;  
   
NAME       NN  
---------- ----------  
test2      B  
test2      C  
test2      D  
test2      E  
 
最后对于求交集用intersect效率高呢还是hash join效率高呢?
[sql] 
SQL> select * from test1 intersect select * from test2;  
   
   
Execution Plan  
----------------------------------------------------------  
Plan hash value: 4290880088  
   
-----------------------------------------------------------------------------  
| Id  | Operation           | Name  | Rows  | Bytes | Cost (%CPU)| Time     |  
-----------------------------------------------------------------------------  
|   0 | SELECT STATEMENT    |       |     5 |   140 |     8  (63)| 00:00:01 |  
|   1 |  INTERSECTION       |       |       |       |            |          |  
|   2 |   SORT UNIQUE       |       |     5 |    70 |     4  (25)| 00:00:01 |  
|   3 |    TABLE ACCESS FULL| TEST1 |     5 |    70 |     3   (0)| 00:00:01 |  
|   4 |   SORT UNIQUE       |       |     5 |    70 |     4  (25)| 00:00:01 |  
|   5 |    TABLE ACCESS FULL| TEST2 |     5 |    70 |     3   (0)| 00:00:01 |  
-----------------------------------------------------------------------------  
   
Note  
-----  
   - dynamic sampling used for this statement (level=2)  
   
   
Statistics 
----------------------------------------------------------  
          0  recursive calls  
          0  db block gets  
         14  consistent gets  
          0  physical reads  
          0  redo size 
        590  bytes sent via SQL*Net to client  
        523  bytes received via SQL*Net from client  
          2  SQL*Net roundtrips to/from client  
          2  sorts (memory)  
          0  sorts (disk)  
          1  rows processed  
   
   
SQL> select a.* from test1 a,test2 b where a.name=b.name and a.nn=b.nn;  
   
   
Execution Plan  
----------------------------------------------------------  
Plan hash value: 497311279  
   
----------------------------------------------------------------------------  
| Id  | Operation          | Name  | Rows  | Bytes | Cost (%CPU)| Time     |  
----------------------------------------------------------------------------  
|   0 | SELECT STATEMENT   |       |     5 |   140 |     7  (15)| 00:00:01 |  
|*  1 |  HASH JOIN         |       |     5 |   140 |     7  (15)| 00:00:01 |  
|   2 |   TABLE ACCESS FULL| TEST1 |     5 |    70 |     3   (0)| 00:00:01 |  
|   3 |   TABLE ACCESS FULL| TEST2 |     5 |    70 |     3   (0)| 00:00:01 |  
----------------------------------------------------------------------------  
   
Predicate Information (identified by operation id):  
---------------------------------------------------  
   
   1 - access("A"."NAME"="B"."NAME" AND "A"."NN"="B"."NN")  
   
Note  
-----  
   - dynamic sampling used for this statement (level=2)  
   
   
Statistics 
----------------------------------------------------------  
          0  recursive calls  
          0  db block gets  
         15  consistent gets  
          0  physical reads  
          0  redo size 
        590  bytes sent via SQL*Net to client  
        523  bytes received via SQL*Net from client  
          2  SQL*Net roundtrips to/from client  
          0  sorts (memory)  
          0  sorts (disk)  
          1  rows processed