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oracle-常見的執行計劃（一），oracle-執行計劃

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oracle-常見的執行計劃（一），oracle-執行計劃

一、表訪問方式

CBO基礎概念中有講到，訪問表的方式有兩種：全表掃描和ROWID掃描。

全表掃描的執行計劃：TABLE ACCESS FULL

ROWID掃描對應執行計劃：TABLE ACCESS BY USER ROWID 或 TABLE ACCESS BY INDEX ROWID

通過例子說明

（一）、全表掃描方式

select empno,ename from scott.emp
      
select *from table(dbms_xplan.display_cursor(null,null))

SQL_ID  6c0fp61y99tuw, child number 0
-------------------------------------
select empno,ename from scott.emp
 
Plan hash value: 3956160932
 
--------------------------------------------------------------------------
| Id  | Operation         | Name | Rows  | Bytes | Cost (%CPU)| Time     |
--------------------------------------------------------------------------
|   0 | SELECT STATEMENT  |      |       |       |     3 (100)|          |
|   1 |  TABLE ACCESS FULL| EMP  |    14 |   140 |     3   (0)| 00:00:01 |
--------------------------------------------------------------------------

（二）、rowid訪問方式

1、TABLE ACCESS BY USER ROWID

select empno,ename from scott.emp where rowid='AAASZHAAEAAAACXAAA'
  
select *from table(dbms_xplan.display_cursor(null,null))

SQL_ID  99f9cvxt33nzy, child number 0
-------------------------------------
select empno,ename from scott.emp where rowid='AAASZHAAEAAAACXAAA'
 
Plan hash value: 1116584662
 
-----------------------------------------------------------------------------------
| Id  | Operation                  | Name | Rows  | Bytes | Cost (%CPU)| Time     |
-----------------------------------------------------------------------------------
|   0 | SELECT STATEMENT           |      |       |       |     1 (100)|          |
|   1 |  TABLE ACCESS BY USER ROWID| EMP  |     1 |    22 |     1   (0)| 00:00:01 |
-----------------------------------------------------------------------------------

2、TABLE ACCESS BY INDEX ROWID

select empno,ename from scott.emp where empno=7521
  
select *from table(dbms_xplan.display_cursor(null,null))

SQL_ID  69nxfycyppq7m, child number 0
-------------------------------------
select empno,ename from scott.emp where empno=7521
 
Plan hash value: 2949544139
 
--------------------------------------------------------------------------------------
| Id  | Operation                   | Name   | Rows  | Bytes | Cost (%CPU)| Time     |
--------------------------------------------------------------------------------------
|   0 | SELECT STATEMENT            |        |       |       |     1 (100)|          |
|   1 |  TABLE ACCESS BY INDEX ROWID| EMP    |     1 |    10 |     1   (0)| 00:00:01 |
|*  2 |   INDEX UNIQUE SCAN         | PK_EMP |     1 |       |     0   (0)|          |
--------------------------------------------------------------------------------------
...

二、B*樹訪問方式

索引唯一掃描、索引范圍掃描、索引全掃描、索引快速掃描、索引跳躍式掃描

以上這些執行計劃執行計劃相對應

索引唯一掃描：INDEX UNIQUE SCAN
索引范圍掃描：INDEX RANGE SCAN
索引全掃描：INDEX FULL SCAN
索引快速全掃描：INDEX FAST FULL SCAN
索引跳躍式掃描：INDEX SKIP SCAN

例子說明

（一）、索引唯一掃描：INDEX UNIQUE SCAN

select empno,ename from scott.emp where empno=7521
  
select *from table(dbms_xplan.display_cursor(null,null))

SQL_ID  69nxfycyppq7m, child number 0
-------------------------------------
select empno,ename from scott.emp where empno=7521
 
Plan hash value: 2949544139
 
--------------------------------------------------------------------------------------
| Id  | Operation                   | Name   | Rows  | Bytes | Cost (%CPU)| Time     |
--------------------------------------------------------------------------------------
|   0 | SELECT STATEMENT            |        |       |       |     1 (100)|          |
|   1 |  TABLE ACCESS BY INDEX ROWID| EMP    |     1 |    10 |     1   (0)| 00:00:01 |
|*  2 |   INDEX UNIQUE SCAN         | PK_EMP |     1 |       |     0   (0)|          |
--------------------------------------------------------------------------------------

通過唯一索引的方式獲取rowid訪問表中的以rowid的方式

（二）、索引范圍掃描：INDEX RANGE SCAN

select empno,ename from scott.emp where empno>=7521 and empno<=8521
  
select *from table(dbms_xplan.display_cursor(null,null))

SQL_ID  95m0uw0yxc10w, child number 0
-------------------------------------
select empno,ename from scott.emp where empno>=7521 and empno<=8521
 
Plan hash value: 169057108
 
--------------------------------------------------------------------------------------
| Id  | Operation                   | Name   | Rows  | Bytes | Cost (%CPU)| Time     |
--------------------------------------------------------------------------------------
|   0 | SELECT STATEMENT            |        |       |       |     2 (100)|          |
|   1 |  TABLE ACCESS BY INDEX ROWID| EMP    |    11 |   110 |     2   (0)| 00:00:01 |
|*  2 |   INDEX RANGE SCAN          | PK_EMP |    11 |       |     1   (0)| 00:00:01 |
--------------------------------------------------------------------------------------
 
Predicate Information (identified by operation id):
---------------------------------------------------
 
   2 - access("EMPNO">=7521 AND "EMPNO"<=8521)

謂詞中存在大於、小於的訪問方式時，並且這個謂詞建議過索引，基本采用索引范圍掃描的方式

（三）、索引全掃描：INDEX FULL SCAN

select empno,ename from scott.emp order by empno

select *from table(dbms_xplan.display_cursor(null,null))

SQL_ID  3bt7b5h1rxh6z, child number 0
-------------------------------------
select empno,ename from scott.emp order by empno
 
Plan hash value: 4170700152
 
--------------------------------------------------------------------------------------
| Id  | Operation                   | Name   | Rows  | Bytes | Cost (%CPU)| Time     |
--------------------------------------------------------------------------------------
|   0 | SELECT STATEMENT            |        |       |       |     2 (100)|          |
|   1 |  TABLE ACCESS BY INDEX ROWID| EMP    |    14 |   140 |     2   (0)| 00:00:01 |
|   2 |   INDEX FULL SCAN           | PK_EMP |    14 |       |     1   (0)| 00:00:01 |
--------------------------------------------------------------------------------------

當索引列的定義可以為null

create index ind_EMP_JOB  ON scott.emp(JOB); 
         
select empno,ename from scott.emp order by job
      
select *from table(dbms_xplan.display_cursor(null,null))

SQL_ID  cnpptzn6mshrb, child number 0
-------------------------------------
select empno,ename from scott.emp order by job
 
Plan hash value: 150391907
 
---------------------------------------------------------------------------
| Id  | Operation          | Name | Rows  | Bytes | Cost (%CPU)| Time     |
---------------------------------------------------------------------------
|   0 | SELECT STATEMENT   |      |       |       |     4 (100)|          |
|   1 |  SORT ORDER BY     |      |    14 |   252 |     4  (25)| 00:00:01 |
|   2 |   TABLE ACCESS FULL| EMP  |    14 |   252 |     3   (0)| 00:00:01 |
---------------------------------------------------------------------------

發現如果JOB列定義可以為空的話，order by 是不會走索引的。

調整列的屬性，不能為空，在查看執行計劃

alter table scott.emp modify(job not null)
          
select empno,ename from scott.emp order by job
      
select *from table(dbms_xplan.display_cursor(null,null))

SQL_ID  cnpptzn6mshrb, child number 0
-------------------------------------
select empno,ename from scott.emp order by job
 
Plan hash value: 157317628
 
-------------------------------------------------------------------------------------------
| Id  | Operation                   | Name        | Rows  | Bytes | Cost (%CPU)| Time     |
-------------------------------------------------------------------------------------------
|   0 | SELECT STATEMENT            |             |       |       |     2 (100)|          |
|   1 |  TABLE ACCESS BY INDEX ROWID| EMP         |    14 |   252 |     2   (0)| 00:00:01 |
|   2 |   INDEX FULL SCAN           | IND_EMP_JOB |    14 |       |     1   (0)| 00:00:01 |
-------------------------------------------------------------------------------------------

（四）、索引快速全掃描：INDEX FAST FULL SCAN

select /*+index_ffs(a ind_EMP_JOB)*/ job  from scott.emp a
      
select *from table(dbms_xplan.display_cursor(null,null))

SQL_ID  3hu16hz75qkhu, child number 0
-------------------------------------
select /*+index_ffs(a ind_EMP_JOB)*/ job  from scott.emp a
 
Plan hash value: 2520590889
 
------------------------------------------------------------------------------------
| Id  | Operation            | Name        | Rows  | Bytes | Cost (%CPU)| Time     |
------------------------------------------------------------------------------------
|   0 | SELECT STATEMENT     |             |       |       |     2 (100)|          |
|   1 |  INDEX FAST FULL SCAN| IND_EMP_JOB |    14 |   112 |     2   (0)| 00:00:01 |
------------------------------------------------------------------------------------

這裡使用HINT，強制提示優化器走fast索引的方式

（五）、索引跳躍式掃描：INDEX SKIP SCAN

用於復合索引中的，非索引前導列的訪問

create index ind_EMP_JENAME  ON scott.emp(JOB,ename); 
          
select empno,ename from scott.emp where ename='ALLEN'

SQL_ID  bdfu46xwtg0qk, child number 0
-------------------------------------
select empno,ename from scott.emp where ename='ALLEN'
 
Plan hash value: 878294805
 
----------------------------------------------------------------------------------------------
| Id  | Operation                   | Name           | Rows  | Bytes | Cost (%CPU)| Time     |
----------------------------------------------------------------------------------------------
|   0 | SELECT STATEMENT            |                |       |       |     2 (100)|          |
|   1 |  TABLE ACCESS BY INDEX ROWID| EMP            |     1 |    10 |     2   (0)| 00:00:01 |
|*  2 |   INDEX SKIP SCAN           | IND_EMP_JENAME |     1 |       |     1   (0)| 00:00:01 |
----------------------------------------------------------------------------------------------
 
Predicate Information (identified by operation id):
---------------------------------------------------
 
   2 - access("ENAME"='ALLEN')
       filter("ENAME"='ALLEN')

三、位圖索引訪問的方式

適用於數據倉庫，不適用OLTP系統，物理存儲結構類似B*數索引，對應rowid的上限、rowid的下限、位圖段。

對於oracle數據庫中的位圖索引而言，他是沒有行鎖這個概念的，要鎖就鎖索引行的整個位圖段，而多個數據行可能對應同一個索引行的位圖段，這個鎖的粒度就決定了位圖索引不適用於高並發並頻繁修改的OLTP系統,在OLTP系統中，很容易產生死鎖。

位圖索引單鍵值掃描：BITMAP INDEX SINGLE VALUE
位圖索引范圍掃描: BITMAP INDEX RANGE SCAN
位圖索引全掃描: BITMAP INDEX FULL SCAN
位圖索引快速全掃描: BITMAP INDEX FAST FULL SCAN
位圖按位與: BITMAP AND
位圖按位或: BITMAP OR
位圖按位減: BITMAP MINUS

（一）、構造一張表，測試位圖索引

Create table test_normal (empno number(10), ename varchar2(30), sal number(10)) TABLESPACE GLL01;

Begin
For i in 1..1000000
Loop
   Insert into test_normal 
   values(i, dbms_random.string('U',30), dbms_random.value(1000,7000));
   If mod(i, 10000) = 0 then
   Commit;
  End if;
End loop;
End;

create bitmap index normal_empno_bmx on test_normal(empno) TABLESPACE GLL01;

create bitmap index normal_empno_sal on test_normal(sal) TABLESPACE GLL01;

EXECUTE DBMS_STATS.GATHER_TABLE_STATS('SYS','TEST_NORMAL',CASCADE=>TRUE);

（二）、位圖索引單鍵值掃描：BITMAP INDEX SINGLE VALUE

select * from test_normal where empno=1000

select *from table(dbms_xplan.display_cursor(null,null))

SQL_ID  343wc0yvq4cc9, child number 0
-------------------------------------
select * from test_normal where empno=1000
 
Plan hash value: 4267925254
 
-------------------------------------------------------------------------------------------------
| Id  | Operation                    | Name             | Rows  | Bytes | Cost (%CPU)| Time     |
-------------------------------------------------------------------------------------------------
|   0 | SELECT STATEMENT             |                  |       |       |     3 (100)|          |
|   1 |  TABLE ACCESS BY INDEX ROWID | TEST_NORMAL      |     1 |    40 |     3   (0)| 00:00:01 |
|   2 |   BITMAP CONVERSION TO ROWIDS|                  |       |       |            |          |
|*  3 |    BITMAP INDEX SINGLE VALUE | NORMAL_EMPNO_BMX |       |       |            |          |
-------------------------------------------------------------------------------------------------
 
Predicate Information (identified by operation id):
---------------------------------------------------
 
   3 - access("EMPNO"=1000)

（三）、位圖索引范圍掃描: BITMAP INDEX RANGE SCAN

select * from  test_normal where empno>=50 and  empno<=2000

select *from table(dbms_xplan.display_cursor(null,null))

SQL_ID  34p69q6q4wqxx, child number 0
-------------------------------------
select * from  test_normal where empno>=50 and  empno<=2000
 
Plan hash value: 641040856
 
-------------------------------------------------------------------------------------------------
| Id  | Operation                    | Name             | Rows  | Bytes | Cost (%CPU)| Time     |
-------------------------------------------------------------------------------------------------
|   0 | SELECT STATEMENT             |                  |       |       |   362 (100)|          |
|   1 |  TABLE ACCESS BY INDEX ROWID | TEST_NORMAL      |  1952 | 78080 |   362   (0)| 00:00:05 |
|   2 |   BITMAP CONVERSION TO ROWIDS|                  |       |       |            |          |
|*  3 |    BITMAP INDEX RANGE SCAN   | NORMAL_EMPNO_BMX |       |       |            |          |
-------------------------------------------------------------------------------------------------
 
Predicate Information (identified by operation id):
---------------------------------------------------
 
   3 - access("EMPNO">=50 AND "EMPNO"<=2000)

（四）、位圖索引全掃描: BITMAP INDEX FULL SCAN

select /*+index(a normal_empno_bmx)*/  a.empno  from  test_normal a

select *from table(dbms_xplan.display_cursor(null,null))

SQL_ID  cmxdf5ry1gvw1, child number 0
-------------------------------------
select /*+index(a normal_empno_bmx)*/  a.empno  from  test_normal a
 
Plan hash value: 220257735
 
------------------------------------------------------------------------------------------------
| Id  | Operation                   | Name             | Rows  | Bytes | Cost (%CPU)| Time     |
------------------------------------------------------------------------------------------------
|   0 | SELECT STATEMENT            |                  |       |       |  3496 (100)|          |
|   1 |  BITMAP CONVERSION TO ROWIDS|                  |  1000K|  4882K|  3496   (1)| 00:00:42 |
|   2 |   BITMAP INDEX FULL SCAN    | NORMAL_EMPNO_BMX |       |       |            |          |
------------------------------------------------------------------------------------------------

（五）、位圖索引快速全掃描: BITMAP INDEX FAST FULL SCAN

select /*+index_ffs(a normal_empno_bmx)*/  a.empno  from  test_normal a

select *from table(dbms_xplan.display_cursor(null,null))

SQL_ID  9rgzkasky186v, child number 0
-------------------------------------
select /*+index_ffs(a normal_empno_bmx)*/  a.empno  from  test_normal a
 
Plan hash value: 2075344169
 
-------------------------------------------------------------------------------------------------
| Id  | Operation                    | Name             | Rows  | Bytes | Cost (%CPU)| Time     |
-------------------------------------------------------------------------------------------------
|   0 | SELECT STATEMENT             |                  |       |       |  3141 (100)|          |
|   1 |  BITMAP CONVERSION TO ROWIDS |                  |  1000K|  4882K|  3141   (1)| 00:00:38 |
|   2 |   BITMAP INDEX FAST FULL SCAN| NORMAL_EMPNO_BMX |       |       |            |          |
-------------------------------------------------------------------------------------------------

（六）、位圖按位與: BITMAP AND、BITMAP OR

select * from  test_normal where empno=3969  and  sal in (1008,1011)

select *from table(dbms_xplan.display_cursor(null,null))

SQL_ID  cyf5th2ts2z7j, child number 0
-------------------------------------
select * from  test_normal where empno=3969  and  sal in (1008,1011)
 
Plan hash value: 640003492
 
--------------------------------------------------------------------------------------------------
| Id  | Operation                     | Name             | Rows  | Bytes | Cost (%CPU)| Time     |
--------------------------------------------------------------------------------------------------
|   0 | SELECT STATEMENT              |                  |       |       |     5 (100)|          |
|   1 |  TABLE ACCESS BY INDEX ROWID  | TEST_NORMAL      |     1 |    40 |     5   (0)| 00:00:01 |
|   2 |   BITMAP CONVERSION TO ROWIDS |                  |       |       |            |          |
|   3 |    BITMAP AND                 |                  |       |       |            |          |
|   4 |     BITMAP OR                 |                  |       |       |            |          |
|*  5 |      BITMAP INDEX SINGLE VALUE| NORMAL_EMPNO_SAL |       |       |            |          |
|*  6 |      BITMAP INDEX SINGLE VALUE| NORMAL_EMPNO_SAL |       |       |            |          |
|*  7 |     BITMAP INDEX SINGLE VALUE | NORMAL_EMPNO_BMX |       |       |            |          |
--------------------------------------------------------------------------------------------------
 
Predicate Information (identified by operation id):
---------------------------------------------------
 
   5 - access("SAL"=1008)
   6 - access("SAL"=1011)
   7 - access("EMPNO"=3969)

（七）、位圖按位減: BITMAP MINUS

select /*+index_ffs(test_normal normal_empno_sal)*/  * from  test_normal where empno>=50 and  empno<=20000 and  sal not in (1008)

select *from table(dbms_xplan.display_cursor(null,null))

SQL_ID  dn3yq5vrp1524, child number 0
-------------------------------------
select /*+index_ffs(test_normal normal_empno_sal)*/  * from  
test_normal where empno>=50 and  empno<=20000 and  sal not in (1008)
 
Plan hash value: 3977516083
 
--------------------------------------------------------------------------------------------------
| Id  | Operation                     | Name             | Rows  | Bytes | Cost (%CPU)| Time     |
--------------------------------------------------------------------------------------------------
|   0 | SELECT STATEMENT              |                  |       |       |  1385 (100)|          |
|   1 |  TABLE ACCESS BY INDEX ROWID  | TEST_NORMAL      | 19949 |   779K|  1385   (1)| 00:00:17 |
|   2 |   BITMAP CONVERSION TO ROWIDS |                  |       |       |            |          |
|   3 |    BITMAP MINUS               |                  |       |       |            |          |
|   4 |     BITMAP MINUS              |                  |       |       |            |          |
|   5 |      BITMAP MERGE             |                  |       |       |            |          |
|*  6 |       BITMAP INDEX RANGE SCAN | NORMAL_EMPNO_BMX |       |       |            |          |
|*  7 |      BITMAP INDEX SINGLE VALUE| NORMAL_EMPNO_SAL |       |       |            |          |
|*  8 |     BITMAP INDEX SINGLE VALUE | NORMAL_EMPNO_SAL |       |       |            |          |
--------------------------------------------------------------------------------------------------
 
Predicate Information (identified by operation id):
---------------------------------------------------
 
   6 - access("EMPNO">=50 AND "EMPNO"<=20000)
   7 - access("SAL"=1008)
   8 - access("SAL" IS NULL)

列值為NULL，位圖索引是記錄，以上這個例子中也把列為NULL剔除

四、表連接的訪問方式

嵌套循環連接：NESTED LOOPS
哈希連接：hash join
排序合並連接：sort join和merge join
反連接：nested loops anti、hash join anti、merge join anti
半連接：nested loop semi、hash join semi、merge join semi

（一）、嵌套循環連接：NESTED LOOPS

select /*+leading(a) use_nl(b)*/* from scott.emp a , scott.dept b  where a.deptno=b.deptno

select *from table(dbms_xplan.display_cursor(null,null))

SQL_ID  c6xax626nhn8k, child number 0
-------------------------------------
select /*+leading(a) use_nl(b)*/* from scott.emp a , scott.dept b  
where a.deptno=b.deptno
 
Plan hash value: 3625962092
 
----------------------------------------------------------------------------------------
| Id  | Operation                    | Name    | Rows  | Bytes | Cost (%CPU)| Time     |
----------------------------------------------------------------------------------------
|   0 | SELECT STATEMENT             |         |       |       |    17 (100)|          |
|   1 |  NESTED LOOPS                |         |       |       |            |          |
|   2 |   NESTED LOOPS               |         |    14 |   798 |    17   (0)| 00:00:01 |
|   3 |    TABLE ACCESS FULL         | EMP     |    14 |   532 |     3   (0)| 00:00:01 |
|*  4 |    INDEX UNIQUE SCAN         | PK_DEPT |     1 |       |     0   (0)|          |
|   5 |   TABLE ACCESS BY INDEX ROWID| DEPT    |     1 |    19 |     1   (0)| 00:00:01 |
----------------------------------------------------------------------------------------
 
Predicate Information (identified by operation id):
---------------------------------------------------
 
   4 - access("A"."DEPTNO"="B"."DEPTNO")

（二）、哈希連接：hash join

select /*+leading(a) use_hash(b)*/* from scott.emp a , scott.dept b  where a.deptno=b.deptno

select *from table(dbms_xplan.display_cursor(null,null))

SQL_ID  fq65sryy1d9dw, child number 0
-------------------------------------
select /*+leading(a) use_hash(b)*/* from scott.emp a , scott.dept b  
where a.deptno=b.deptno
 
Plan hash value: 1123238657
 
---------------------------------------------------------------------------
| Id  | Operation          | Name | Rows  | Bytes | Cost (%CPU)| Time     |
---------------------------------------------------------------------------
|   0 | SELECT STATEMENT   |      |       |       |     7 (100)|          |
|*  1 |  HASH JOIN         |      |    14 |   798 |     7  (15)| 00:00:01 |
|   2 |   TABLE ACCESS FULL| EMP  |    14 |   532 |     3   (0)| 00:00:01 |
|   3 |   TABLE ACCESS FULL| DEPT |     3 |    57 |     3   (0)| 00:00:01 |
---------------------------------------------------------------------------
 
Predicate Information (identified by operation id):
---------------------------------------------------
 
   1 - access("A"."DEPTNO"="B"."DEPTNO")

（三）、排序合並連接：sort join和merge join

select /*+use_merge(a b)*/* from scott.emp a , scott.dept b  where a.deptno=b.deptno

select *from table(dbms_xplan.display_cursor(null,null))

SQL_ID  9w06suya2pdrn, child number 0
-------------------------------------
select /*+use_merge(a b)*/* from scott.emp a , scott.dept b  where 
a.deptno=b.deptno
 
Plan hash value: 844388907
 
----------------------------------------------------------------------------------------
| Id  | Operation                    | Name    | Rows  | Bytes | Cost (%CPU)| Time     |
----------------------------------------------------------------------------------------
|   0 | SELECT STATEMENT             |         |       |       |     6 (100)|          |
|   1 |  MERGE JOIN                  |         |    14 |   798 |     6  (17)| 00:00:01 |
|   2 |   TABLE ACCESS BY INDEX ROWID| DEPT    |     3 |    57 |     2   (0)| 00:00:01 |
|   3 |    INDEX FULL SCAN           | PK_DEPT |     3 |       |     1   (0)| 00:00:01 |
|*  4 |   SORT JOIN                  |         |    14 |   532 |     4  (25)| 00:00:01 |
|   5 |    TABLE ACCESS FULL         | EMP     |    14 |   532 |     3   (0)| 00:00:01 |
----------------------------------------------------------------------------------------
 
Predicate Information (identified by operation id):
---------------------------------------------------
 
   4 - access("A"."DEPTNO"="B"."DEPTNO")
       filter("A"."DEPTNO"="B"."DEPTNO")

（四）、反連接：nested loops anti

alter table scott.emp modify(deptno not  null)

select * from scott.emp  a WHERE A.DEPTNO NOT   IN (SELECT  /*+nl_aj*/  DEPTNO FROM scott.dept b where a.deptno=b.deptno)

select *from table(dbms_xplan.display_cursor(null,null))

SQL_ID  dh1c9mwpw9pjx, child number 0
-------------------------------------
select * from scott.emp  a WHERE A.DEPTNO NOT   IN (SELECT  /*+nl_aj*/  
DEPTNO FROM scott.dept b where a.deptno=b.deptno)
 
Plan hash value: 3496123964
 
------------------------------------------------------------------------------
| Id  | Operation          | Name    | Rows  | Bytes | Cost (%CPU)| Time     |
------------------------------------------------------------------------------
|   0 | SELECT STATEMENT   |         |       |       |     3 (100)|          |
|   1 |  NESTED LOOPS ANTI |         |     7 |   287 |     3   (0)| 00:00:01 |
|   2 |   TABLE ACCESS FULL| EMP     |    14 |   532 |     3   (0)| 00:00:01 |
|*  3 |   INDEX UNIQUE SCAN| PK_DEPT |     2 |     6 |     0   (0)|          |
------------------------------------------------------------------------------
 
Predicate Information (identified by operation id):
---------------------------------------------------
 
   3 - access("A"."DEPTNO"="B"."DEPTNO")

（五）、反連接：hash join anti

select * from scott.emp a WHERE A.DEPTNO NOT  IN (SELECT /*+hash_aj*/    DEPTNO FROM scott.dept b where a.deptno=b.deptno)

select *from table(dbms_xplan.display_cursor(null,null))

SQL_ID  dhq4hhqgqqn0n, child number 0
-------------------------------------
select * from scott.emp a WHERE A.DEPTNO NOT  IN (SELECT /*+hash_aj*/   
 DEPTNO FROM scott.dept b where a.deptno=b.deptno)
 
Plan hash value: 1958379418
 
------------------------------------------------------------------------------
| Id  | Operation          | Name    | Rows  | Bytes | Cost (%CPU)| Time     |
------------------------------------------------------------------------------
|   0 | SELECT STATEMENT   |         |       |       |     5 (100)|          |
|*  1 |  HASH JOIN ANTI    |         |     7 |   287 |     5  (20)| 00:00:01 |
|   2 |   TABLE ACCESS FULL| EMP     |    14 |   532 |     3   (0)| 00:00:01 |
|   3 |   INDEX FULL SCAN  | PK_DEPT |     3 |     9 |     1   (0)| 00:00:01 |
------------------------------------------------------------------------------
 
Predicate Information (identified by operation id):
---------------------------------------------------
 
   1 - access("A"."DEPTNO"="B"."DEPTNO")

（六）、反連接：merge join anti

select * from scott.emp  a WHERE A.DEPTNO NOT   IN (SELECT  /*+merge_aj*/  DEPTNO FROM scott.dept b where a.deptno=b.deptno)

select *from table(dbms_xplan.display_cursor(null,null))

SQL_ID  1r60ktudp9vq2, child number 0
-------------------------------------
select * from scott.emp  a WHERE A.DEPTNO NOT   IN (SELECT  
/*+merge_aj*/  DEPTNO FROM scott.dept b where a.deptno=b.deptno)
 
Plan hash value: 4267419248
 
-------------------------------------------------------------------------------
| Id  | Operation           | Name    | Rows  | Bytes | Cost (%CPU)| Time     |
-------------------------------------------------------------------------------
|   0 | SELECT STATEMENT    |         |       |       |     6 (100)|          |
|   1 |  MERGE JOIN ANTI    |         |     7 |   287 |     6  (34)| 00:00:01 |
|   2 |   SORT JOIN         |         |    14 |   532 |     4  (25)| 00:00:01 |
|   3 |    TABLE ACCESS FULL| EMP     |    14 |   532 |     3   (0)| 00:00:01 |
|*  4 |   SORT UNIQUE       |         |     3 |     9 |     2  (50)| 00:00:01 |
|   5 |    INDEX FULL SCAN  | PK_DEPT |     3 |     9 |     1   (0)| 00:00:01 |
-------------------------------------------------------------------------------
 
Predicate Information (identified by operation id):
---------------------------------------------------
 
   4 - access("A"."DEPTNO"="B"."DEPTNO")
       filter("A"."DEPTNO"="B"."DEPTNO")

（七）、半連接：nested loop semi

select * from scott.emp a WHERE  EXISTS (SELECT /*+nl_sj*/  1 FROM scott.dept b where a.deptno=b.deptno)

select *from table(dbms_xplan.display_cursor(null,null))

SQL_ID  9htytj0pxjhkg, child number 0
-------------------------------------
select * from scott.emp a WHERE  EXISTS (SELECT /*+nl_sj*/  1 FROM 
scott.dept b where a.deptno=b.deptno)
 
Plan hash value: 3274513678
 
------------------------------------------------------------------------------
| Id  | Operation          | Name    | Rows  | Bytes | Cost (%CPU)| Time     |
------------------------------------------------------------------------------
|   0 | SELECT STATEMENT   |         |       |       |     3 (100)|          |
|   1 |  NESTED LOOPS SEMI |         |     7 |   287 |     3   (0)| 00:00:01 |
|   2 |   TABLE ACCESS FULL| EMP     |    14 |   532 |     3   (0)| 00:00:01 |
|*  3 |   INDEX UNIQUE SCAN| PK_DEPT |     2 |     6 |     0   (0)|          |
------------------------------------------------------------------------------
 
Predicate Information (identified by operation id):
---------------------------------------------------
 
   3 - access("A"."DEPTNO"="B"."DEPTNO")

（八）、半連接：hash join semi

select * from scott.emp a WHERE  EXISTS (SELECT /*+hash_sj*/  1 FROM scott.dept b where a.deptno=b.deptno)

select *from table(dbms_xplan.display_cursor(null,null))

SQL_ID  cjhjgkgs8q1fc, child number 0
-------------------------------------
select * from scott.emp a WHERE  EXISTS (SELECT /*+hash_sj*/  1 FROM 
scott.dept b where a.deptno=b.deptno)
 
Plan hash value: 3753861400
 
------------------------------------------------------------------------------
| Id  | Operation          | Name    | Rows  | Bytes | Cost (%CPU)| Time     |
------------------------------------------------------------------------------
|   0 | SELECT STATEMENT   |         |       |       |     5 (100)|          |
|*  1 |  HASH JOIN SEMI    |         |     7 |   287 |     5  (20)| 00:00:01 |
|   2 |   TABLE ACCESS FULL| EMP     |    14 |   532 |     3   (0)| 00:00:01 |
|   3 |   INDEX FULL SCAN  | PK_DEPT |     3 |     9 |     1   (0)| 00:00:01 |
------------------------------------------------------------------------------
 
Predicate Information (identified by operation id):
---------------------------------------------------
 
   1 - access("A"."DEPTNO"="B"."DEPTNO")

（九）、半連接：merge join semi

select * from scott.emp a WHERE  EXISTS (SELECT /*+merge_sj*/  1 FROM scott.dept b where a.deptno=b.deptno)

select *from table(dbms_xplan.display_cursor(null,null))

SQL_ID  f2zxcjpqvpsu5, child number 0
-------------------------------------
select * from scott.emp a WHERE  EXISTS (SELECT /*+merge_sj*/  1 FROM 
scott.dept b where a.deptno=b.deptno)
 
Plan hash value: 3011744318
 
-------------------------------------------------------------------------------
| Id  | Operation           | Name    | Rows  | Bytes | Cost (%CPU)| Time     |
-------------------------------------------------------------------------------
|   0 | SELECT STATEMENT    |         |       |       |     6 (100)|          |
|   1 |  MERGE JOIN SEMI    |         |     7 |   287 |     6  (34)| 00:00:01 |
|   2 |   SORT JOIN         |         |    14 |   532 |     4  (25)| 00:00:01 |
|   3 |    TABLE ACCESS FULL| EMP     |    14 |   532 |     3   (0)| 00:00:01 |
|*  4 |   SORT UNIQUE       |         |     3 |     9 |     2  (50)| 00:00:01 |
|   5 |    INDEX FULL SCAN  | PK_DEPT |     3 |     9 |     1   (0)| 00:00:01 |
-------------------------------------------------------------------------------
 
Predicate Information (identified by operation id):
---------------------------------------------------
 
   4 - access("A"."DEPTNO"="B"."DEPTNO")
       filter("A"."DEPTNO"="B"."DEPTNO")