Lesson 37 : Pseudocolumn - ROWNUM

Pseudocolumn  - ROWNUM

For each row returned by a query, the ROWNUM pseudocolumn returns a number indicating the order in which Oracle 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.

You can use ROWNUM to limit the number of rows returned by a query, as in this example:

Example :

SQL> select rownum,name from employee;

    ROWNUM NAME

---------- ----------

         1 John

         2 Devy

         3 Paul

         4 Raj

         5 Chetan

         6 Jayne

         7 Senthil

         8 Jeya

 

8 rows selected.

 

SQL> select rownum,name from employee order by name;

 

    ROWNUM NAME

---------- ----------

         5 Chetan

         2 Devy

         6 Jayne

         8 Jeya

         1 John

         3 Paul

         4 Raj

         7 Senthil

 

8 rows selected.

 

SQL> select rownum,name from employee where rownum < 5;

 

    ROWNUM NAME

---------- ----------

         1 John

         2 Devy

         3 Paul

         4 Raj

 

SQL> select rownum,name from employee where rownum = 5;

 

no rows selected