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Problem: I need write stored procedure(s) that will return result set of a single page of rows and the number of total rows.

Solution A: I create two stored procedures, one that returns a results set of a single page and another that returns a scalar -- total rows. The Explain Plan says the first sproc has a cost of 9 and the second has a cost of 3.

SELECT * FROM ( SELECT ROW_NUMBER() OVER ( ORDER BY D.ID DESC ) AS RowNum, ... ) AS PageResult WHERE RowNum >= @from AND RowNum < @to ORDER BY RowNum SELECT COUNT(*) FROM ...

Solution B: I put everything in a single sproc, by adding the same TotalRows number to every row in the result set. This solution feel hackish, but has a cost of 9 and only one sproc, so I'm inclined to use this solution.

SELECT * FROM ( SELECT ROW_NUMBER() OVER ( ORDER BY D.ID DESC ) RowNum, COUNT(*) OVER () TotalRows, WHERE RowNum >= from AND RowNum < to ORDER BY RowNum;

Is there a best-practice for pagination in Oracle? Which of the aforementioned solutions is most used in practice? Is any of them considered just plain wrong? Note that my DB is and will stay relatively small (less than 10GB).

I'm using Oracle 11g and the latest ODP.NET with VS2010 SP1 and Entity Framework 4.4. I need the final solution to work within the EF 4.4. I'm sure there are probably better methods out there for pagination in general, but I need them working with EF.

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    Pagination in EF is database agnostic. Commented Dec 6, 2012 at 6:36
  • Yeah, but I just wanted to make it clear, that I don't want to use ODP.NET- or ADO.NET-specific code, but would rather stay on high-level. Commented Dec 6, 2012 at 6:44
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    Tom Kyte wrote an article on limiting resultsets using rownum: oracle.com/technetwork/issue-archive/2006/06-sep/… It may answer some of your questions. Commented Dec 6, 2012 at 7:37

7 Answers 7

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If you're already using analytics (ROW_NUMBER() OVER ...) then adding another analytic function on the same partitioning will add a negligible cost to the query.

On the other hand, there are many other ways to do pagination, one of them using rownum:

SELECT * FROM (SELECT A.*, rownum rn FROM (SELECT * FROM your_table ORDER BY col) A WHERE rownum <= :Y) WHERE rn >= :X

This method will be superior if you have an appropriate index on the ordering column. In this case, it might be more efficient to use two queries (one for the total number of rows, one for the result).

Both methods are appropriate but in general if you want both the number of rows and a pagination set then using analytics is more efficient because you only query the rows once.

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8 Comments

See Tom Kyte "On ROWNUM and Limiting Results" in Oracle Magazine (Sept/Oct 2006).
I have issues with syntax * followed by comma on second line. Doesn't seem to like syntax. You need A.* instead, then A after col)
Why did u filtered rownum in two queries instead of one? Could be "WHERE rownum <= :Y AND rownum >= :X". Does it gives poor performance?
@IúridosAnjos: The Tom Kyte article suggested by Ludovic Kuty explains why it wouldn't work: rownum >= 2 is always FALSE
@IúridosAnjos: the inner SELECT is used to sort and can not contain ROWNUM because ROWNUM is computed before sorting. Here's an example with dbfiddle. Of course it's also explained in the Oracle Magazine article which I once more encourage you to read :)
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In Oracle 12C you can use limit LIMIT and OFFSET for the pagination.

Example - Suppose you have Table tab from which data needs to be fetched on the basis of DATE datatype column dt in descending order using pagination.

page_size:=5 select * from tab order by dt desc OFFSET nvl(page_no-1,1)*page_size ROWS FETCH NEXT page_size ROWS ONLY;

Explanation:

page_no=1 page_size=5

OFFSET 0 ROWS FETCH NEXT 5 ROWS ONLY - Fetch 1st 5 rows only

page_no=2 page_size=5

OFFSET 5 ROWS FETCH NEXT 5 ROWS ONLY - Fetch next 5 rows

and so on.

Refrence Pages -

https://dba-presents.com/index.php/databases/oracle/31-new-pagination-method-in-oracle-12c-offset-fetch

https://oracle-base.com/articles/12c/row-limiting-clause-for-top-n-queries-12cr1#paging

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The sad thing is the lack of COUNT(*) as some sort of variable o built-in column with the total records with the given criteria. I understand that it could cost, but developers will do it anyway in order to determine how many pages we have in total.
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This may help:

 SELECT * FROM ( SELECT deptno, ename, sal, ROW_NUMBER() OVER (ORDER BY ename) Row_Num FROM emp) WHERE Row_Num BETWEEN 5 and 10;
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This is exactly what the OP has in the question... you'll have to explain why it will help as the OP is looking for the most performant solution. Why is this better than using rownum and in what situations? Do you have any benchmarks?
Well, this is how I understood the question. I hope I got it right. The diff between ROWNUM and ROW_NUMBER() (in Oracle) is that first is pseudocolumn and last is analytic function. You can use both. But the ROWNUM is not always work with ORDER BY.Try adding Order by with ROWNUM and you will see the difference. And using analytic functions is best and up to date and generally improves the performance. You can read more about ROWNUM and ROW_NUMBER() in documentation. Thank you.
Yes, you're correct. The rownum predicate will return a random value when used in conjuction with an ORDER BY unless the ordering is done inside a sub-select. However, my point was that your answer does not answer the question. It was a comment on whether it would work. Analytic functions though "recent" are, in this case, not necessarily more efficient than rownum as they require additional scans of the table whereas rownum does not (as explained in Vincent's answer).
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A clean way to organize your SQL code could be trough WITH statement.

The reduced version implements also total number of results and total pages count.

For example

WITH SELECTION AS ( SELECT FIELDA, FIELDB, FIELDC FROM TABLE), NUMBERED AS ( SELECT ROW_NUMBER() OVER (ORDER BY FIELDA) RN, SELECTION.* FROM SELECTION) SELECT (SELECT COUNT(*) FROM NUMBERED) TOTAL_ROWS, NUMBERED.* FROM NUMBERED WHERE RN BETWEEN ((:page_size*:page_number)-:page_size+1) AND (:page_size*:page_number)

This code gives you a paged resultset with two more fields:

  • TOTAL_ROWS with the total rows of your full SELECTION
  • RN the row number of the record

It requires 2 parameter: :page_size and :page_number to slice your SELECTION

Reduced Version

Selection implements already ROW_NUMBER() field

WITH SELECTION AS ( SELECT ROW_NUMBER() OVER (ORDER BY FIELDA) RN, FIELDA, FIELDB, FIELDC FROM TABLE) SELECT :page_number PAGE_NUMBER, CEIL((SELECT COUNT(*) FROM SELECTION ) / :page_size) TOTAL_PAGES, :page_size PAGE_SIZE, (SELECT COUNT(*) FROM SELECTION ) TOTAL_ROWS, SELECTION.* FROM SELECTION WHERE RN BETWEEN ((:page_size*:page_number)-:page_size+1) AND (:page_size*:page_number)
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Try this:

select * from ( select * from "table" order by "column" desc ) where ROWNUM > 0 and ROWNUM <= 5;
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Good answers accompany code samples with an explanation for future readers. While the person asking this question may understand your answer, explaining how you arrived at it will help countless others.
hmm... doesn't work if I change rownum > 0 to rownum > 1. I don't know why for now...
@PavelBiryukov for why that doesn't work see: blogs.oracle.com/connect/post/on-rownum-and-limiting-results
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I also faced a similar issue. I tried all the above solutions and none gave me a better performance. I have a table with millions of records and I need to display them on screen in pages of 20. I have done the below to solve the issue.

  1. Add a new column ROW_NUMBER in the table.
  2. Make the column as primary key or add a unique index on it.
  3. Use the population program (in my case, Informatica), to populate the column with rownum.
  4. Fetch Records from the table using between statement. (SELECT * FROM TABLE WHERE ROW_NUMBER BETWEEN LOWER_RANGE AND UPPER_RANGE).

This method is effective if we need to do an unconditional pagination fetch on a huge table.

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Sorry, this one works with sorting:

SELECT * FROM (SELECT ROWNUM rnum,a.* FROM (SELECT * FROM "tabla" order by "column" asc) a) WHERE rnum BETWEEN "firstrange" AND "lastrange";
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