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