leading--Oracle hint
SQL> explain plan for select rowid rid from
2 scott.emp e where e.empno >100 and e.empno < 1000 and e.deptno in (select deptno from scott.dept where dname like 'a%');
已解释。
SQL> SELECT * FROM TABLE(DBMS_XPLAN.DISPLAY(NULL, NULL, 'ADVANCED -PROJECTION'));
PLAN_TABLE_OUTPUT
----------------------------------------------------------------------------------------------------------------------------------------
Plan hash value: 1465018025 -----------------------------------------------------------------------------------------
| Id | Operation | Name | Rows | Bytes | Cost (%CPU)| Time |
-----------------------------------------------------------------------------------------
| 0 | SELECT STATEMENT | | 1 | 32 | 3 (0)| 00:00:01 |
| 1 | NESTED LOOPS | | | | | |
| 2 | NESTED LOOPS | | 1 | 32 | 3 (0)| 00:00:01 |
| 3 | TABLE ACCESS BY INDEX ROWID| EMP | 1 | 19 | 2 (0)| 00:00:01 |
|* 4 | INDEX RANGE SCAN | PK_EMP | 1 | | 1 (0)| 00:00:01 |
|* 5 | INDEX UNIQUE SCAN | PK_DEPT | 1 | | 0 (0)| 00:00:01 |
|* 6 | TABLE ACCESS BY INDEX ROWID | DEPT | 1 | 13 | 1 (0)| 00:00:01 |
----------------------------------------------------------------------------------------- Query Block Name / Object Alias (identified by operation id):
------------------------------------------------------------- 1 - SEL$5DA710D3
3 - SEL$5DA710D3 / E@SEL$1
4 - SEL$5DA710D3 / E@SEL$1
5 - SEL$5DA710D3 / DEPT@SEL$2
6 - SEL$5DA710D3 / DEPT@SEL$2 Outline Data
------------- /*+
BEGIN_OUTLINE_DATA
NLJ_BATCHING(@"SEL$5DA710D3" "DEPT"@"SEL$2")
USE_NL(@"SEL$5DA710D3" "DEPT"@"SEL$2")
LEADING(@"SEL$5DA710D3" "E"@"SEL$1" "DEPT"@"SEL$2")
INDEX(@"SEL$5DA710D3" "DEPT"@"SEL$2" ("DEPT"."DEPTNO"))
INDEX_RS_ASC(@"SEL$5DA710D3" "E"@"SEL$1" ("EMP"."EMPNO"))
OUTLINE(@"SEL$2")
OUTLINE(@"SEL$1")
UNNEST(@"SEL$2")
OUTLINE_LEAF(@"SEL$5DA710D3")
ALL_ROWS
DB_VERSION('11.2.0.1')
OPTIMIZER_FEATURES_ENABLE('11.2.0.1')
IGNORE_OPTIM_EMBEDDED_HINTS
END_OUTLINE_DATA
*/ Predicate Information (identified by operation id):
--------------------------------------------------- 4 - access("E"."EMPNO">100 AND "E"."EMPNO"<)
5 - access("E"."DEPTNO"="DEPTNO")
6 - filter("DNAME" LIKE 'a%')
已选择50行。
SQL> explain plan for select /*+leading(DEPT@SEL$2)*/rowid rid from
2 scott.emp e where e.empno >100 and e.empno < 1000 and e.deptno in (select deptno from scott.dept where dname like 'a%');
已解释。
SQL> SELECT * FROM TABLE(DBMS_XPLAN.DISPLAY(NULL, NULL, 'ADVANCED -PROJECTION'));
PLAN_TABLE_OUTPUT
----------------------------------------------------------------------------------------------------------------------------------------
Plan hash value: 817787759 -----------------------------------------------------------------------------------------
| Id | Operation | Name | Rows | Bytes | Cost (%CPU)| Time |
-----------------------------------------------------------------------------------------
| 0 | SELECT STATEMENT | | 1 | 32 | 5 (20)| 00:00:01 |
| 1 | MERGE JOIN | | 1 | 32 | 5 (20)| 00:00:01 |
|* 2 | TABLE ACCESS BY INDEX ROWID | DEPT | 1 | 13 | 2 (0)| 00:00:01 |
| 3 | INDEX FULL SCAN | PK_DEPT | 4 | | 1 (0)| 00:00:01 |
|* 4 | SORT JOIN | | 1 | 19 | 3 (34)| 00:00:01 |
| 5 | TABLE ACCESS BY INDEX ROWID| EMP | 1 | 19 | 2 (0)| 00:00:01 |
|* 6 | INDEX RANGE SCAN | PK_EMP | 1 | | 1 (0)| 00:00:01 |
----------------------------------------------------------------------------------------- Query Block Name / Object Alias (identified by operation id):
------------------------------------------------------------- 1 - SEL$5DA710D3
2 - SEL$5DA710D3 / DEPT@SEL$2
3 - SEL$5DA710D3 / DEPT@SEL$2
5 - SEL$5DA710D3 / E@SEL$1
6 - SEL$5DA710D3 / E@SEL$1 Outline Data
------------- /*+
BEGIN_OUTLINE_DATA
USE_MERGE(@"SEL$5DA710D3" "E"@"SEL$1")
LEADING(@"SEL$5DA710D3" "DEPT"@"SEL$2" "E"@"SEL$1")
INDEX_RS_ASC(@"SEL$5DA710D3" "E"@"SEL$1" ("EMP"."EMPNO"))
INDEX(@"SEL$5DA710D3" "DEPT"@"SEL$2" ("DEPT"."DEPTNO"))
OUTLINE(@"SEL$2")
OUTLINE(@"SEL$1")
UNNEST(@"SEL$2")
OUTLINE_LEAF(@"SEL$5DA710D3")
ALL_ROWS
DB_VERSION('11.2.0.1')
OPTIMIZER_FEATURES_ENABLE('11.2.0.1')
IGNORE_OPTIM_EMBEDDED_HINTS
END_OUTLINE_DATA
*/ Predicate Information (identified by operation id):
--------------------------------------------------- 2 - filter("DNAME" LIKE 'a%')
4 - access("E"."DEPTNO"="DEPTNO")
filter("E"."DEPTNO"="DEPTNO")
6 - access("E"."EMPNO">100 AND "E"."EMPNO"<) 已选择50行。
SQL> explain plan for select /*+leading(DEPT)*/rowid rid from
2 scott.emp e where e.empno >100 and e.empno < 1000 and e.deptno in (select deptno from scott.dept where dname like 'a%');
已解释。
SQL> SELECT * FROM TABLE(DBMS_XPLAN.DISPLAY(NULL, NULL, 'ADVANCED -PROJECTION'));
PLAN_TABLE_OUTPUT
----------------------------------------------------------------------------------------------------------------------------------------
Plan hash value: 817787759 -----------------------------------------------------------------------------------------
| Id | Operation | Name | Rows | Bytes | Cost (%CPU)| Time |
-----------------------------------------------------------------------------------------
| 0 | SELECT STATEMENT | | 1 | 32 | 5 (20)| 00:00:01 |
| 1 | MERGE JOIN | | 1 | 32 | 5 (20)| 00:00:01 |
|* 2 | TABLE ACCESS BY INDEX ROWID | DEPT | 1 | 13 | 2 (0)| 00:00:01 |
| 3 | INDEX FULL SCAN | PK_DEPT | 4 | | 1 (0)| 00:00:01 |
|* 4 | SORT JOIN | | 1 | 19 | 3 (34)| 00:00:01 |
| 5 | TABLE ACCESS BY INDEX ROWID| EMP | 1 | 19 | 2 (0)| 00:00:01 |
|* 6 | INDEX RANGE SCAN | PK_EMP | 1 | | 1 (0)| 00:00:01 |
----------------------------------------------------------------------------------------- Query Block Name / Object Alias (identified by operation id):
------------------------------------------------------------- 1 - SEL$5DA710D3
2 - SEL$5DA710D3 / DEPT@SEL$2
3 - SEL$5DA710D3 / DEPT@SEL$2
5 - SEL$5DA710D3 / E@SEL$1
6 - SEL$5DA710D3 / E@SEL$1 Outline Data
------------- /*+
BEGIN_OUTLINE_DATA
USE_MERGE(@"SEL$5DA710D3" "E"@"SEL$1")
LEADING(@"SEL$5DA710D3" "DEPT"@"SEL$2" "E"@"SEL$1")
INDEX_RS_ASC(@"SEL$5DA710D3" "E"@"SEL$1" ("EMP"."EMPNO"))
INDEX(@"SEL$5DA710D3" "DEPT"@"SEL$2" ("DEPT"."DEPTNO"))
OUTLINE(@"SEL$2")
OUTLINE(@"SEL$1")
UNNEST(@"SEL$2")
OUTLINE_LEAF(@"SEL$5DA710D3")
ALL_ROWS
DB_VERSION('11.2.0.1')
OPTIMIZER_FEATURES_ENABLE('11.2.0.1')
IGNORE_OPTIM_EMBEDDED_HINTS
END_OUTLINE_DATA
*/ Predicate Information (identified by operation id):
--------------------------------------------------- 2 - filter("DNAME" LIKE 'a%')
4 - access("E"."DEPTNO"="DEPTNO")
filter("E"."DEPTNO"="DEPTNO")
6 - access("E"."EMPNO">100 AND "E"."EMPNO"<) 已选择50行。
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