--SQL2，优化后
SQL> with b as (select count(1) from test where object_id<10),
c as (select count(1) from test where object_id>=10 and object_id<20)
select (select * from b) bc,
(select * from c) cc
from dual;
执行计划
----------------------------------------------------------
Plan hash value: 1155001961
--------------------------------------------------------------------------------------
| Id | Operation | Name | Rows | Bytes | Cost (%CPU)| Time |
--------------------------------------------------------------------------------------
| 0 | SELECT STATEMENT | | 1 | | 2 (0)| 00:00:01 |
| 1 | VIEW | | 1 | 13 | 2 (0)| 00:00:01 |
| 2 | SORT AGGREGATE | | 1 | 5 | | |
|* 3 | INDEX RANGE SCAN| IND_T_OBJECT_ID | 6 | 30 | 2 (0)| 00:00:01 |
| 4 | VIEW | | 1 | 13 | 2 (0)| 00:00:01 |
| 5 | SORT AGGREGATE | | 1 | 5 | | |
|* 6 | INDEX RANGE SCAN| IND_T_OBJECT_ID | 9 | 45 | 2 (0)| 00:00:01 |
| 7 | FAST DUAL | | 1 | | 2 (0)| 00:00:01 |
--------------------------------------------------------------------------------------
Predicate Information (identified by operation id):
---------------------------------------------------
3 - access("OBJECT_ID"<10)
6 - access("OBJECT_ID">=10 AND "OBJECT_ID"<20)
统计信息
----------------------------------------------------------
1 recursive calls
0 db block gets
4 consistent gets
0 physical reads
0 redo size
381 bytes sent via SQL*Net to client
337 bytes received via SQL*Net from client
2 SQL*Net roundtrips to/from client
0 sorts (memory)
0 sorts (disk)
1 rows processed
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