Can i use an analytic function instead of a group by clause?

Question

Can i use an analytic function instead of a group by clause? Will this help in any performance improvement?

Answer 1

analytic can sometimes avoid scanning the table more than once :
SQL> select ename,  sal, (select sum(sal) from emp where deptno=e.deptno) sum from emp e;
ENAME             SAL        SUM
SMITH             800      10875
ALLEN            1600       9400
WARD             1250       9400
JONES            2975      10875
MARTIN           1250       9400
BLAKE            2850       9400
CLARK            2450       8750
SCOTT            3000      10875
KING             5000       8750
TURNER           1500       9400
ADAMS            1100      10875
JAMES             950       9400
FORD             3000      10875
MILLER           1300       8750
14 rows selected.
Execution Plan
Plan hash value: 3189885365
| Id  | Operation          | Name | Rows  | Bytes | Cost (%CPU)| Time     |
|   0 | SELECT STATEMENT   |      |    14 |   182 |     3   (0)| 00:00:01 |
|   1 |  SORT AGGREGATE    |      |     1 |     7 |            |          |
|*  2 |   TABLE ACCESS FULL| EMP  |     5 |    35 |     3   (0)| 00:00:01 |
|   3 |  TABLE ACCESS FULL | EMP  |    14 |   182 |     3   (0)| 00:00:01 |
Predicate Information (identified by operation id):
   2 - filter("DEPTNO"=:B1)which could be rewritten as
SQL> select ename, sal, sum(sal) over (partition by deptno) sum from emp e;
ENAME             SAL        SUM
CLARK            2450       8750
KING             5000       8750
MILLER           1300       8750
JONES            2975      10875
FORD             3000      10875
ADAMS            1100      10875
SMITH             800      10875
SCOTT            3000      10875
WARD             1250       9400
TURNER           1500       9400
ALLEN            1600       9400
JAMES             950       9400
BLAKE            2850       9400
MARTIN           1250       9400
14 rows selected.
Execution Plan
Plan hash value: 1776581816
| Id  | Operation          | Name | Rows  | Bytes | Cost (%CPU)| Time     |
|   0 | SELECT STATEMENT   |      |    14 |   182 |     4  (25)| 00:00:01 |
|   1 |  WINDOW SORT       |      |    14 |   182 |     4  (25)| 00:00:01 |
|   2 |   TABLE ACCESS FULL| EMP  |    14 |   182 |     3   (0)| 00:00:01 |
---------------------------------------------------------------------------well, there is no group by and no visible performance enhancement in my example, but Oracle7, you must have written the query as :
SQL> select ename, sal, sum from emp e,(select deptno,sum(sal) sum from emp group by deptno) s where e.deptno=s.deptno;
ENAME             SAL        SUM
SMITH             800      10875
ALLEN            1600       9400
WARD             1250       9400
JONES            2975      10875
MARTIN           1250       9400
BLAKE            2850       9400
CLARK            2450       8750
SCOTT            3000      10875
KING             5000       8750
TURNER           1500       9400
ADAMS            1100      10875
JAMES             950       9400
FORD             3000      10875
MILLER           1300       8750
14 rows selected.
Execution Plan
Plan hash value: 2661063502
| Id  | Operation            | Name | Rows  | Bytes | Cost (%CPU)| Time     |
|   0 | SELECT STATEMENT     |      |    14 |   546 |     8  (25)| 00:00:01 |
|*  1 |  HASH JOIN           |      |    14 |   546 |     8  (25)| 00:00:01 |
|   2 |   VIEW               |      |     3 |    78 |     4  (25)| 00:00:01 |
|   3 |    HASH GROUP BY     |      |     3 |    21 |     4  (25)| 00:00:01 |
|   4 |     TABLE ACCESS FULL| EMP  |    14 |    98 |     3   (0)| 00:00:01 |
|   5 |   TABLE ACCESS FULL  | EMP  |    14 |   182 |     3   (0)| 00:00:01 |
-----------------------------------------------------------------------------So maybe it helps