Analytic Functions in Oracle (10g)

Oracle Analytic Functions

Analyctic functions in Oracle are set of functions and clauses used for arriving statistical informations like sum, average. These functions are more flexible to use and efficient.

Examples: Calculate a running total and moving average, Top-N queries

Earlier, these problems were solved using PL/SQL. But wehn we look for better performance, PL/SQL does not benefit much. Analytical functions provides more benifits with no questions on performance.Though this feature has been intrduced from Oracle 8, many developers does not aware of this. Especially for a pivot table query most of the developers still going for the old approach.

Key benefits

  • Easier to code
  • Faster than a equivalent SQL or PL/SQL
  • No need to test or tune for performance as in the case of custom SQL/PL-SQL

Syntax

<Analytic-Function>(parameter1,parameter2,...)

OVER (

<Partition By column1, column2, .. [Order By column1, column2, .. [ASC/DESC] [NULLS FIRST/LAST] ] >

Order By

Order By column1, column2, .. [ASC/DESC] [NULLS FIRST/LAST]

[ROWS [UNBOUNDED] v_rows PRECEDING/FOLLOWING] / [RANGE [UNBOUNDED] v_range PRECEDING/FOLLOWING]

)

Note: The ROWS/RANGE keywords are called windowing clauses/windowing functions.
 

List of Analytic-Functions

AVG, CORR, COVAR_POP, COVAR_SAMP, COUNT, CUME_DIST, DENSE_RANK, FIRST, FIRST_VALUE, LAG, LAST, LAST_VALUE, LEAD, MAX, MIN, NTILE, PERCENT_RANK, PERCENTILE_CONT, PERCENTILE_DISC, RANK, RATIO_TO_REPORT, STDDEV, STDDEV_POP, STDDEV_SAMP, SUM, VAR_POP, VAR_SAMP, VARIANCE.

Example-1: Top-n Query using Oracle Analytic Functions

Below query pulls out top-3 ranked sales figures department wise. Query uses a partition by clause over DENSE_RANK function.

 
SELECT * FROM
(SELECT sale_date, dept_code, sales_amount,
DENSE_RANK() OVER(PARTITION BY DEPT_CODE ORDER BY SALES_AMOUNT DESC) sale_rank
FROM sales_summary_daily)
WHERE sale_rank <=3;
 
 
Below is the resuts of the query. 
 
SALE_DATE DEPT_CODE 	SALES_AMOUNT 	SALE_RANK 
--------- --------- 	--------------  ---------------------- 
28-OCT-03 East 		99998.63	1 
19-SEP-95 East 		99996.64 	2 
08-OCT-85 East 		99942.49 	3 
06-NOV-98 NE 		49995.44 	1 
15-FEB-06 NE 		49991.96 	2 
28-DEC-98 NE 		49988.92 	3 
09-FEB-05 North 	99983.69 	1 
24-DEC-86 North 	99980.99 	2 
22-OCT-02 North 	99973.49 	3 
16-APR-82 SE 		49998.3 	1 
27-JAN-95 SE 		49996.16 	2
14-SEP-83 SE 		49990.52 	3
27-JUL-96 South 	69996.2 	1
15-JAN-06 South 	69993.7 	2
17-AUG-97 South 	69991.29 	3
10-OCT-96 West 		9999.91 	1
23-AUG-94 West 		9998.76 	2
06-SEP-02 West 		9998.51 	3
 
Above query pulls top-3 sales figures for all sales region 
using Oracle analytic functions. Deriving this using 
conventional SQL/PLSQL will be a night mare.

Example-2 Pivot Table Query using Oracle Analytic Functions

SELECT SALE_MONTH, 
MAX(DECODE(sale_rank, 1, dept_code, null)) First,
MAX(DECODE(sale_rank, 2, dept_code, null)) Second,
MAX(DECODE(sale_rank, 3, dept_code, null)) Third
FROM
(SELECT LAST_DAY(SALE_DATE) SALE_MONTH, dept_code, sales_amount,
DENSE_RANK() OVER(PARTITION BY LAST_DAY(SALE_DATE)
ORDER BY SALES_AMOUNT DESC) sale_rank
FROM sales_summary_daily
WHERE SALE_DATE >= '01-JAN-2008'
)
WHERE SALE_RANK <= 3
GROUP BY SALE_MONTH
 
 
SALE_MONTH 	FIRST SECOND THIRD 
--------------- ----- ------ ----- 
31-JAN-08 	North North  North 
29-FEB-08 	North East   North 
30-APR-08 	East  North  East 
30-JUN-08 	North North  North 
31-JUL-08 	East  North  North 
31-AUG-08 	North East   North 
31-MAR-08 	North North  East 
31-MAY-08 	North North  East 
30-SEP-08 	East  North  North 
 

Again using conventional SQL/PLSQL needs more effort to make it efficient. With Oracle 11g, this is even more simplified using the pivot operator.

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Comments 10 comments

Guna 7 years ago

Very useful, handy and simple samples. i am looking for this for a while. Thanks for such a good article.


John 6 years ago

Hi,

Read your article. Brilliant job!!

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Sandeep 6 years ago

Thanks for the article, was so helpful


Cicil  6 years ago

Excellent lead into a deep subject . Thank you .


nallapati 6 years ago

thanks


M.A.Anwar 6 years ago

I think, row_number(),rank() and dense_rank()wonderful function. I like these most.


Omkar 6 years ago

It is really helpful sample. Thanks for such a nice article


Oracle Recovery 5 years ago

Very Nice Article.

Thanx for sharing


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giteshtrivedi 5 years ago from USA

Excellent tips and informative article. Appreciate sharing.


selvirajan profile image

selvirajan 5 months ago from India Author

Back here after few years. Glad that still this helped many people.

Thanks to all the viewers who made this interactive while i am away. Would try to catch up slowly and regularly.

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