测试验证
如下SQL：
select *
from (select *
from (select a.*, rownum rn
from (select
*
from test
where owner like 'SYS%'
and object_id > 1000
order by object_name) a)
where rownum <= 10)
where rn >= 1;有like模糊过滤条件，有非等值过滤条件，有排序。
创建索引：
测试1：
SQL> create index idx_name_id on test(object_name,object_id);
Index created.
SQL> select * from table(dbms_xplan.display_cursor(null,null,'allstats last'));
PLAN_TABLE_OUTPUT
--------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------
SQL_ID 6h95n2pg07f77, child number 0
-------------------------------------
select * from (select * from (select a.*, rownum rn
from (select /*+index(test idx_name_id)*/
* from test
where owner like 'SYS%' and object_id >
1000 order by object_name) a) where
rownum <= 10) where rn >= 1
Plan hash value: 1798652263
------------------------------------------------------------------------------------------------------------------
| Id | Operation | Name | Starts | E-Rows | A-Rows | A-Time | Buffers | Reads |
------------------------------------------------------------------------------------------------------------------
| 0 | SELECT STATEMENT | | 1 | | 10 |00:00:00.01 | 19 | 5 |
|* 1 | VIEW | | 1 | 10 | 10 |00:00:00.01 | 19 | 5 |
|* 2 | COUNT STOPKEY | | 1 | | 10 |00:00:00.01 | 19 | 5 |
| 3 | VIEW | | 1 | 35003 | 10 |00:00:00.01 | 19 | 5 |
| 4 | COUNT | | 1 | | 10 |00:00:00.01 | 19 | 5 |
| 5 | VIEW | | 1 | 35003 | 10 |00:00:00.01 | 19 | 5 |
|* 6 | TABLE ACCESS BY INDEX ROWID| TEST | 1 | 35003 | 10 |00:00:00.01 | 19 | 5 |
|* 7 | INDEX FULL SCAN | IDX_NAME_ID | 1 | 72571 | 23 |00:00:00.01 | 4 | 5 |
------------------------------------------------------------------------------------------------------------------
Predicate Information (identified by operation id):
---------------------------------------------------
1 - filter("RN">=1)
2 - filter(ROWNUM<=10)
6 - filter("OWNER" LIKE 'SYS%')
7 - access("OBJECT_ID">1000)
filter("OBJECT_ID">1000)测试2：
SQL> create index idx_name_id_owner on test(object_name,object_id,owner);
Index created.
SQL> select * from table(dbms_xplan.display_cursor(null,null,'allstats last'));
PLAN_TABLE_OUTPUT
--------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------
SQL_ID bs0qhcj9p45hp, child number 0
-------------------------------------
select * from (select * from (select a.*, rownum rn
from (select /*+index(test idx_name_id_owner)*/
* from test
where owner like 'SYS%' and object_id >
1000 order by object_name) a) where
rownum <= 10) where rn >= 1
Plan hash value: 810954641
-----------------------------------------------------------------------------------------------------------------------
| Id | Operation | Name | Starts | E-Rows | A-Rows | A-Time | Buffers | Reads |
-----------------------------------------------------------------------------------------------------------------------
| 0 | SELECT STATEMENT | | 1 | | 10 |00:00:00.01 | 14 | 5 |
|* 1 | VIEW | | 1 | 10 | 10 |00:00:00.01 | 14 | 5 |
|* 2 | COUNT STOPKEY | | 1 | | 10 |00:00:00.01 | 14 | 5 |
| 3 | VIEW | | 1 | 35003 | 10 |00:00:00.01 | 14 | 5 |
| 4 | COUNT | | 1 | | 10 |00:00:00.01 | 14 | 5 |
| 5 | VIEW | | 1 | 35003 | 10 |00:00:00.01 | 14 | 5 |
| 6 | TABLE ACCESS BY INDEX ROWID| TEST | 1 | 35003 | 10 |00:00:00.01 | 14 | 5 |
|* 7 | INDEX FULL SCAN | IDX_NAME_ID_OWNER | 1 | 35003 | 10 |00:00:00.01 | 4 | 5 |
-----------------------------------------------------------------------------------------------------------------------
Predicate Information (identified by operation id):
---------------------------------------------------
1 - filter("RN">=1)
2 - filter(ROWNUM<=10)
7 - access("OBJECT_ID">1000 AND "OWNER" LIKE 'SYS%')
filter(("OWNER" LIKE 'SYS%' AND "OBJECT_ID">1000))测试3：
SQL> create index idx_name_owner_id on test(object_name,owner,object_id);
Index created.
SQL> select * from table(dbms_xplan.display_cursor(null,null,'allstats last'));
PLAN_TABLE_OUTPUT
--------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------
SQL_ID du0qd7phsxnc6, child number 0
-------------------------------------
select * from (select * from (select a.*, rownum rn
from (select /*+index(test idx_name_owner_id)*/
* from test
where owner like 'SYS%' and object_id >
1000 order by object_name) a) where
rownum <= 10) where rn >= 1
Plan hash value: 1258538393
-----------------------------------------------------------------------------------------------------------------------
| Id | Operation | Name | Starts | E-Rows | A-Rows | A-Time | Buffers | Reads |
-----------------------------------------------------------------------------------------------------------------------
| 0 | SELECT STATEMENT | | 1 | | 10 |00:00:00.01 | 14 | 2 |
|* 1 | VIEW | | 1 | 10 | 10 |00:00:00.01 | 14 | 2 |
|* 2 | COUNT STOPKEY | | 1 | | 10 |00:00:00.01 | 14 | 2 |
| 3 | VIEW | | 1 | 35003 | 10 |00:00:00.01 | 14 | 2 |
| 4 | COUNT | | 1 | | 10 |00:00:00.01 | 14 | 2 |
| 5 | VIEW | | 1 | 35003 | 10 |00:00:00.01 | 14 | 2 |
| 6 | TABLE ACCESS BY INDEX ROWID| TEST | 1 | 35003 | 10 |00:00:00.01 | 14 | 2 |
|* 7 | INDEX FULL SCAN | IDX_NAME_OWNER_ID | 1 | 35003 | 10 |00:00:00.01 | 4 | 2 |
-----------------------------------------------------------------------------------------------------------------------
Predicate Information (identified by operation id):
---------------------------------------------------
1 - filter("RN">=1)
2 - filter(ROWNUM<=10)
7 - access("OWNER" LIKE 'SYS%' AND "OBJECT_ID">1000)
filter(("OWNER" LIKE 'SYS%' AND "OBJECT_ID">1000))从上面三个执行计划可以看到，当过滤条件中有like时，非等值过滤，排序时，应该将排序列放在索引最前面，like和非等值过滤列放后面，二者之间顺序可以互换。
