few useful features in Oracle

1. Few Useful Features
Heribertus Bramundito

2. Analytical Function
 Ranking
 RANK, DENSE_RANK, CUME_DIST, PERCENT_RANK,
NTILE, ROW_NUMBER
 LAG and LEAD
 FIRST_VALUE and LAST_VALUE
 FIRST and LAST
 Windowing
 Reporting
 Most of aggregate function can be user (MAX, MIN, AVG,
SUM, COUNT)

3. Ranking (RANK, DENSE_RANK,
CUME_DIST)

4. Ranking (PERCENT_RANK, NTILE,
ROW_NUMBER)

5. LEAD and LAG

6. FIRST_VALUE and LAST VALUE

7. FIRST and LAST

8. Windowing

9. Windowing (cont.)

10. Windowing (cont.)

11. Reporting (RATIO_TO_REPORT)

12. Hypothetical Rank

13. Flashback
 Flashback query
 Flashback version query
 Flashback transaction query
 Flashback Table
 Flashback Drop

14. Flashback Query

15. Flashback Query (cont.)

16. Flashback Version Query

17. Flashback Transaction Query
 Query flashback_transaction_query view

18. Flashback Table
 Row Movement should be enabled

19. Flashback Drop

20. Rewrite Query – Correlated Sub-Query
Check logical
I/O

21. Rewrite Query – IN vs EXISTS
 Not In and Not Exists will produces exactly the same result if
there is no NULL record in the sub-query. Extra predicate can be
added for NULL value checking.
 Not Exists is more efficient because when Oracle found 1 record
that satisfied the condition in the Sub-Query, it will move to the
next record of Main Query and also Oracle will be able to use
index in Sub-Query.
 In case of Not In, Oracle has to scan whole population of SubQuery before it move to the next record of Main Query. It will
takes more IO and because of implicit NVL function in the
predicate, Oracle will not be able to use index access.
 Not In will be translated as ((COL != VALUE_1) AND (COL !=
VALUE_2) AND (COL != VALUE_3) … AND (COL !=
VALUE_X))

22. Log Mining
 Collection of procedure to read an examine redo log or
archive log
 Database Supplemental Log Data should be turn on.