oraclehint有效范围是什么
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hint的范围
parameter hints对整个sql有效率，其它hints只对单个查询块起作用，要在查询块内指定hints
当子查询，内联view时候会有多个查询块，要为每个查询块 加hint控制该查询块（hint有效范围控制在查询块内）
SQL> create table t1 (a int,b varchar2(10));
Table created.
SQL> create table t2 (a2 int,b2 varchar2(10));
Table created.
SQL>
SQL> insert into t1 values(1,'a');
1 row created.
SQL> insert into t2 values(1,'b');
1 row created.
SQL> commit;
Commit complete.
SQL> create index t1_id on t1(a);
Index created.
SQL> create index t2_id on t2(a2);
Index created.
SQL> execute dbms_stats.gather_table_stats('XH','T1');
PL/SQL procedure successfully completed.
SQL> execute dbms_stats.gather_table_stats('XH','T2');
PL/SQL procedure successfully completed.
SQL> set autotrace trace exp
SQL> select * from t1 where a=(select a2 from t2 where a2=1 );
Execution Plan
----------------------------------------------------------
Plan hash value: 3305116341
-------------------------------------------------------------------------------------
| Id | Operation | Name | Rows | Bytes | Cost (%CPU)| Time |
-------------------------------------------------------------------------------------
| 0 | SELECT STATEMENT | | 1 | 5 | 3 (0)| 00:00:01 |
| 1 | TABLE ACCESS BY INDEX ROWID| T1 | 1 | 5 | 2 (0)| 00:00:01 |
|* 2 | INDEX RANGE SCAN | T1_ID | 1 | | 1 (0)| 00:00:01 |
|* 3 | INDEX RANGE SCAN | T2_ID | 1 | 3 | 1 (0)| 00:00:01 |
-------------------------------------------------------------------------------------
Predicate Information (identified by operation id):
---------------------------------------------------
2 - access("A"= (SELECT "A2" FROM "T2" "T2" WHERE "A2"=1))
3 - access("A2"=1)
SQL> select /*+full(t1)*/ * from t1 where a=(select a2 from t2 where a2=1 );
Execution Plan
----------------------------------------------------------
Plan hash value: 1681039550
---------------------------------------------------------------------------
| Id | Operation | Name | Rows | Bytes | Cost (%CPU)| Time |
---------------------------------------------------------------------------
| 0 | SELECT STATEMENT | | 1 | 5 | 4 (0)| 00:00:01 |
|* 1 | TABLE ACCESS FULL| T1 | 1 | 5 | 3 (0)| 00:00:01 |
|* 2 | INDEX RANGE SCAN| T2_ID | 1 | 3 | 1 (0)| 00:00:01 |
---------------------------------------------------------------------------
Predicate Information (identified by operation id):
---------------------------------------------------
1 - filter("A"= (SELECT "A2" FROM "T2" "T2" WHERE "A2"=1))
2 - access("A2"=1)
全局hint使用.引用包含在其他查询块中的对象(引用的查询块已经有别名才行,查询块别名 不是表别名)
SQL> select * from t1 ts where a=(select /*+full(t2) full(ts.t1)*/a2 from t2 where a2=1 );
Execution Plan
----------------------------------------------------------
Plan hash value: 2910250514
-------------------------------------------------------------------------------------
| Id | Operation | Name | Rows | Bytes | Cost (%CPU)| Time |
-------------------------------------------------------------------------------------
| 0 | SELECT STATEMENT | | 1 | 5 | 5 (0)| 00:00:01 |
| 1 | TABLE ACCESS BY INDEX ROWID| T1 | 1 | 5 | 2 (0)| 00:00:01 |
|* 2 | INDEX RANGE SCAN | T1_ID | 1 | | 1 (0)| 00:00:01 |
|* 3 | TABLE ACCESS FULL | T2 | 1 | 3 | 3 (0)| 00:00:01 |
-------------------------------------------------------------------------------------
Predicate Information (identified by operation id):
---------------------------------------------------
2 - access("A"= (SELECT /*+ FULL ("T2") */ "A2" FROM "T2" "T2" WHERE
"A2"=1))
3 - filter("A2"=1)
SQL> with
2 t1_t as (select * from t1)
3 select t1_t.a,t2.b2 from t2,t1_t where t2.a2=t1_t.a
4 /
Execution Plan
----------------------------------------------------------
Plan hash value: 978323357
--------------------------------------------------------------------------------------
| Id | Operation | Name | Rows | Bytes | Cost (%CPU)| Time |
--------------------------------------------------------------------------------------
| 0 | SELECT STATEMENT | | 1 | 8 | 2 (0)| 00:00:01 |
| 1 | NESTED LOOPS | | | | | |
| 2 | NESTED LOOPS | | 1 | 8 | 2 (0)| 00:00:01 |
| 3 | INDEX FULL SCAN | T1_ID | 1 | 3 | 1 (0)| 00:00:01 |
|* 4 | INDEX RANGE SCAN | T2_ID | 1 | | 0 (0)| 00:00:01 |
| 5 | TABLE ACCESS BY INDEX ROWID| T2 | 1 | 5 | 1 (0)| 00:00:01 |
--------------------------------------------------------------------------------------
Predicate Information (identified by operation id):
---------------------------------------------------
4 - access("T2"."A2"="T1"."A")
SQL> with
2 t1_t as (select * from t1)
3 select/*+full(t2) full(t1_t.t1)*/ t1_t.a,t2.b2 from t2,t1_t where t2.a2=t1_t.a
4 /
Execution Plan
----------------------------------------------------------
Plan hash value: 2959412835
---------------------------------------------------------------------------
| Id | Operation | Name | Rows | Bytes | Cost (%CPU)| Time |
---------------------------------------------------------------------------
| 0 | SELECT STATEMENT | | 1 | 8 | 7 (15)| 00:00:01 |
|* 1 | HASH JOIN | | 1 | 8 | 7 (15)| 00:00:01 |
| 2 | TABLE ACCESS FULL| T2 | 1 | 5 | 3 (0)| 00:00:01 |
| 3 | TABLE ACCESS FULL| T1 | 1 | 3 | 3 (0)| 00:00:01 |
---------------------------------------------------------------------------
Predicate Information (identified by operation id):
---------------------------------------------------
1 - access("T2"."A2"="T1"."A")
SQL>
假如子查询没有别名，可以制作一个别名为子查询(用qb_name hint制作),10g才能用qb_name
SQL> with
2 t1_t as (select /*+qb_name(sq)*/ * from t1)
3 select /*+qb_name(sq_t) full(@sq t1) full(@sq_t t2)*/ t1_t.a,t2.b2 from t2,t1_t where t2.a2=t1_t.a
4 /
Execution Plan
----------------------------------------------------------
Plan hash value: 2959412835
---------------------------------------------------------------------------
| Id | Operation | Name | Rows | Bytes | Cost (%CPU)| Time |
---------------------------------------------------------------------------
| 0 | SELECT STATEMENT | | 1 | 8 | 7 (15)| 00:00:01 |
|* 1 | HASH JOIN | | 1 | 8 | 7 (15)| 00:00:01 |
| 2 | TABLE ACCESS FULL| T2 | 1 | 5 | 3 (0)| 00:00:01 |
| 3 | TABLE ACCESS FULL| T1 | 1 | 3 | 3 (0)| 00:00:01 |
---------------------------------------------------------------------------
Predicate Information (identified by operation id):
---------------------------------------------------
1 - access("T2"."A2"="T1"."A")
SQL> SQL> select /*+qb_name(sq) full(@sq t1) full(@sq_t t2)*/* from t1 where a=(select /*+qb_name(sq_t)*/ a2 from t2 where a2=1);
Execution Plan
----------------------------------------------------------
Plan hash value: 1484901111
---------------------------------------------------------------------------
| Id | Operation | Name | Rows | Bytes | Cost (%CPU)| Time |
---------------------------------------------------------------------------
| 0 | SELECT STATEMENT | | 1 | 5 | 6 (0)| 00:00:01 |
|* 1 | TABLE ACCESS FULL | T1 | 1 | 5 | 3 (0)| 00:00:01 |
|* 2 | TABLE ACCESS FULL| T2 | 1 | 3 | 3 (0)| 00:00:01 |
---------------------------------------------------------------------------
Predicate Information (identified by operation id):
---------------------------------------------------
1 - filter("A"= (SELECT /*+ QB_NAME ("SQ_T") FULL ("T2") */ "A2"
FROM "T2" "T2" WHERE "A2"=1))
2 - filter("A2"=1)
SQL> SQL> select /*+qb_name(sq)*/* from t1 where a=(select /*+qb_name(sq_t) full(@sq t1) full(@sq_t t2)*/ a2 from t2 where a2=1);
Execution Plan
----------------------------------------------------------
Plan hash value: 1484901111
---------------------------------------------------------------------------
| Id | Operation | Name | Rows | Bytes | Cost (%CPU)| Time |
---------------------------------------------------------------------------
| 0 | SELECT STATEMENT | | 1 | 5 | 6 (0)| 00:00:01 |
|* 1 | TABLE ACCESS FULL | T1 | 1 | 5 | 3 (0)| 00:00:01 |
|* 2 | TABLE ACCESS FULL| T2 | 1 | 3 | 3 (0)| 00:00:01 |
---------------------------------------------------------------------------
Predicate Information (identified by operation id):
---------------------------------------------------
1 - filter("A"= (SELECT /*+ QB_NAME ("SQ_T") FULL ("T2") */ "A2"
FROM "T2" "T2" WHERE "A2"=1))
2 - filter("A2"=1)
使用query optimizer生成的别名
SQL> explain plan set statement_id='xh' for select * from t1 where a=(select a2 from t2 where a2=1);
Explained.
SQL> select * from table(dbms_xplan.display(null,'xh','basic +alias'));
PLAN_TABLE_OUTPUT
------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------
Plan hash value: 3305116341
---------------------------------------------
| Id | Operation | Name |
---------------------------------------------
| 0 | SELECT STATEMENT | |
| 1 | TABLE ACCESS BY INDEX ROWID| T1 |
| 2 | INDEX RANGE SCAN | T1_ID |
| 3 | INDEX RANGE SCAN | T2_ID |
---------------------------------------------
PLAN_TABLE_OUTPUT
------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------
Query Block Name / Object Alias (identified by operation id):
-------------------------------------------------------------
1 - SEL$1 / T1@SEL$1
2 - SEL$1 / T1@SEL$1
3 - SEL$2 / T2@SEL$2
17 rows selected.
SEL$为查询块前缀名（sel=select,cri$=create index,del$=delete,ins$=insert,misc$=lock table或多类语句,mrg$=merge,set$=union&minus,upd$=update）
顺序是按sql语句parse阶段查询块出现位置(左-右)，所以sel$1表示 select t1那个 查询块，sel$2 表示select t2那个查询块
SQL> select * from t1 where a=(select /*+full(@sel$2 t2) full(@sel$1 t1)*/a2 from t2 where a2=1 );
Execution Plan
----------------------------------------------------------
Plan hash value: 1484901111
---------------------------------------------------------------------------
| Id | Operation | Name | Rows | Bytes | Cost (%CPU)| Time |
---------------------------------------------------------------------------
| 0 | SELECT STATEMENT | | 1 | 5 | 6 (0)| 00:00:01 |
|* 1 | TABLE ACCESS FULL | T1 | 1 | 5 | 3 (0)| 00:00:01 |
|* 2 | TABLE ACCESS FULL| T2 | 1 | 3 | 3 (0)| 00:00:01 |
---------------------------------------------------------------------------
Predicate Information (identified by operation id):
---------------------------------------------------
1 - filter("A"= (SELECT /*+ FULL ("T2") */ "A2" FROM "T2" "T2" WHERE
"A2"=1))
2 - filter("A2"=1)
另外表有别名的话hint中要用别名
SQL> select * from t1 ts where a=(select /*+full(@sel$2 t2) full(@sel$1 ts)*/a2 from t2 where a2=1 );
Execution Plan
----------------------------------------------------------
Plan hash value: 1484901111
---------------------------------------------------------------------------
| Id | Operation | Name | Rows | Bytes | Cost (%CPU)| Time |
---------------------------------------------------------------------------
| 0 | SELECT STATEMENT | | 1 | 5 | 6 (0)| 00:00:01 |
|* 1 | TABLE ACCESS FULL | T1 | 1 | 5 | 3 (0)| 00:00:01 |
|* 2 | TABLE ACCESS FULL| T2 | 1 | 3 | 3 (0)| 00:00:01 |
---------------------------------------------------------------------------
Predicate Information (identified by operation id):
---------------------------------------------------
1 - filter("A"= (SELECT /*+ FULL ("T2") */ "A2" FROM "T2" "T2" WHERE
"A2"=1))
2 - filter("A2"=1)
*另外parameter hints对整个sql有效率(例如hint all_rows,gather_plan_statistics之类)
*11g中v$sql_hint可以查看可以使用的hint列表
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