Go4Oracle

rownum a pseudocolumn

(0 votes)

Written by ankur
Sunday, 14 September 2008

Rownum :- Rownum is a pseudocolumns. A pseudocolumn behaves like a table column but is not actually stored in the table. You cannot insert or delete values of the pseudocolumns.

For each row returned by a query, the ROWNUM pseudocolumn returns a number indicating the order in which Oracle server selects the row from a table or set of joined rows. The first row selected has a ROWNUM of 1, the second has 2, and so on.Rownum can be used to limit the number of rows retieved.

Example

SELECT empno, ename, job FROM emp WHERE ROWNUM < 5;

Output

empno | ename | job

7521 | WARD | SALESMAN

7566 | JONES | MANAGER

7654 | MARTIN | SALESMAN

7698 | BLAKE | MANAGER

(4 rows)

Free social bookmarking plugins and extensions for Joomla! websites! title=

Users' Comments

Average user rating

(0 vote)

Display 1 of 1 comments

[+] Expand comment

rownum are very usefula feature

By: amal (Registered) on 05-10-2008 19:15

[-] Collapse comment

rownum are very usefula feature

By: amal (Registered ) on 05-10-2008 19:15

rownums can also be used for exceptions handling...a simple case may be in a PLSQL Exception too_many_rows.
Eg. Select col into variable from tablename
where colname = 'Some Values' this can return multiple records and we can come across exception too_many_rows....
If we modify the above with following then we are assured that the plsql statement will never encounter too_many_rows exception

Select col into variable from tablename
where colname = 'Some Values'
and rownum =1

Display 1 of 1 comments

Add your comment

[+] Show form

[-] Hide form