LEFT JOINT OUTER has diferent plan from normal query

Question

Hi All
I have two table TRANS and TRANS_PARTY, on trans table has index on LAST_MODIFIED and on trans_party has index on transid
I have two queries. They are the same about meaning but Oracle has different plan.
Can anyone explain the reason why?
SQL> explain plan for select count(*) from trans t1t
2 LEFT OUTER JOIN trans_party t1tp ON
(t1t.id=t1tp.transid AND t1t.last_modified >=to_date('2009-09-04 00:00:00','YYYY-MM-DD HH24:MI:SS')
AND t1t.last_modified <to_date('2009-09-05 00:00:00','YYYY-MM-DD HH24:MI:SS')
and t1tp.last_modified >=to_date('2009-09-04 00:00:00','YYYY-MM-DD HH24:MI:SS')
AND t1tp.last_modified <to_date('2009-09-05 00:00:00','YYYY-MM-DD HH24:MI:SS'))
3 4 5 6 7 ;
Explained.
SQL>
SQL> set pagesize 999;
set linesize 999;SQL>
SQL>
SQL> SELECT * FROM TABLE(dbms_xplan.display);
PLAN_TABLE_OUTPUT
Plan hash value: 2040563577
| Id | Operation | Name | Rows | Bytes | Cost (%CPU)| Time |
| 0 | SELECT STATEMENT | | 1 | 17 | 275K (1)| 00:55:07 |
| 1 | SORT AGGREGATE | | 1 | 17 | | |
| 2 | NESTED LOOPS OUTER | | 1233K| 19M| 275K (1)| 00:55:07 |
| 3 | TABLE ACCESS FULL | TRANS | 1233K| 19M| 4085 (3)| 00:00:50 |
| 4 | VIEW | | 1 | | 0 (0)| 00:00:01 |
|* 5 | FILTER | | | | | |
|* 6 | TABLE ACCESS BY INDEX ROWID| TRANS_PARTY | 1 | 17 | 1 (0)| 00:00:01 |
|* 7 | INDEX RANGE SCAN | IXTPFK | 1 | | 1 (0)| 00:00:01 |
Predicate Information (identified by operation id):
5 - filter("T1T"."LAST_MODIFIED"<TIMESTAMP'2009-09-05 00:00:00' AND
"T1T"."LAST_MODIFIED">=TIMESTAMP'2009-09-04 00:00:00')
6 - filter("T1TP"."LAST_MODIFIED">=TIMESTAMP'2009-09-04 00:00:00' AND
"T1TP"."LAST_MODIFIED"<TIMESTAMP'2009-09-05 00:00:00')
7 - access("T1T"."ID"="T1TP"."TRANSID")
23 rows selected.
SQL> explain plan for select count(*) from trans t , trans_party tp
where t.id(+)=tp.transid
and t.last_modified >=to_date('2009-09-04 00:00:00','YYYY-MM-DD HH24:MI:SS')
AND t.last_modified <to_date('2009-09-05 00:00:00','YYYY-MM-DD HH24:MI:SS')
and (tp.agentid=2654492 OR tp.agentid=2654492) 2 3 4 5 ;
Explained.
SQL> SELECT * FROM TABLE(dbms_xplan.display);
PLAN_TABLE_OUTPUT
Plan hash value: 1553247449
| Id | Operation | Name | Rows | Bytes | Cost (%CPU)| Time | Pstart| Pstop |
| 0 | SELECT STATEMENT | | 1 | 31 | 3 (0)| 00:00:01 | | |
| 1 | SORT AGGREGATE | | 1 | 31 | | | | |
|* 2 | TABLE ACCESS BY LOCAL INDEX ROWID | TRANS_PARTY | 1 | 13 | 1 (0)| 00:00:01 | | |
| 3 | NESTED LOOPS | | 1 | 31 | 3 (0)| 00:00:01 | | |
| 4 | PARTITION RANGE ALL | | 1 | 18 | 1 (0)| 00:00:01 | 1 | 71 |
| 5 | TABLE ACCESS BY LOCAL INDEX ROWID| TRANS | 1 | 18 | 1 (0)| 00:00:01 | 1 | 71 |
|* 6 | INDEX RANGE SCAN | IXTRLASTMOD | 1 | | 1 (0)| 00:00:01 | 1 | 71 |
| 7 | PARTITION RANGE ALL | | 3 | | 1 (0)| 00:00:01 | 1 | 71 |
|* 8 | INDEX RANGE SCAN | IXTPFK | 3 | | 1 (0)| 00:00:01 | 1 | 71 |
Predicate Information (identified by operation id):
2 - filter("TP"."AGENTID"=2654492)
6 - access("T"."LAST_MODIFIED">=TIMESTAMP' 2009-09-04 00:00:00' AND "T"."LAST_MODIFIED"<TIMESTAMP'
2009-09-05 00:00:00')
8 - access("T"."ID"="TP"."TRANSID")
23 rows selected.
SQL>
Thanks
Edited by: user554265 on Sep 7, 2009 7:13 AM

Answer 1

Toon Koppelaars wrote:
My advice: stop using the ANSI SQL syntax for doing (outer) joins.
It is confusing.
It is hard to read.
It is hard to understand.Hmmm... blatent statements and no proof.
I'm adept at using either syntax.
ANSI is not confusing to me, it's quite the opposite. Therefore your view that it's confusing is just that... your view.
Hard to read? Actually, I find that it clarifies the join conditions from the clauses and makes outer joins easier to specify. Again, that's your view.
Hard to understand? Nah, I can understand both just as easily. What's hard about it?
Also bear in mind...
Oracle syntax does not support outer joining to more than one table.
However ANSI syntax does...
SQL> select * from a;
        ID      B_KEY      C_KEY
         1          2          3
         2          1          4
         3          3          1
         4          4          2
SQL> select * from b;
        ID     C_KEY2
         1          1
         2          5
         3          3
         4          2
SQL> select * from c;
      KEY1       KEY2 DTA
         1          1 1-1
         1          2 1-2
         1          3 1-3
         1          4 1-4
         2          1 2-1
         2          2 2-2
         2          3 2-3
         2          4 2-4
         3          1 3-1
         3          2 3-2
         3          3 3-3
         3          4 3-4
         4          1 4-1
         4          2 4-2
         4          3 4-3
         4          4 4-4
16 rows selected.
SQL> ed
Wrote file afiedt.buf
  1  select a.id as a_id, b.id as b_id, c.key1 as c_key1, c.key2 as c_key3, c.dta
  2  from a, b, c
  3  where a.b_key = b.id
  4  and   a.c_key = c.key1 (+)
  5* and   b.c_key2 = c.key2 (+)
SQL> /
and   a.c_key = c.key1 (+)
ERROR at line 4:
ORA-01417: a table may be outer joined to at most one other table
SQL> ed
Wrote file afiedt.buf
  1  select a.id as a_id, b.id as b_id, c.key1 as c_key1, c.key2 as c_key3, c.dta
  2  from a JOIN b ON (a.b_key = b.id)
  3*        LEFT OUTER JOIN c ON (a.c_key = c.key1 and b.c_key2 = c.key2)
SQL> /
      A_ID       B_ID     C_KEY1     C_KEY3 DTA
         3          3          1          3 1-3
         4          4          2          2 2-2
         2          1          4          1 4-1
         1          2
SQL>;)