Sampling a certain percent of rows from a table!

Hi,

Can someone explain the following. The total number of rows in the table is 14. So sampling 50% should always give me a count of 7, right? But notice that it shows different outputs for the same same query. Am I being mistaken somewhere?

SQL> select count(*) from emp;

  COUNT(*)

        14

SQL> select count(*) from emp sample(50);

  COUNT(*)

         6

SQL> select count(*) from emp sample(50);

  COUNT(*)

         7

SQL> select count(*) from emp sample(50);

  COUNT(*)

         7

SQL> select count(*) from emp sample(50);

  COUNT(*)

         7

SQL> select count(*) from emp sample(50);

  COUNT(*)

         8

Thanks,
A$!f. Received on Sat Jan 24 2004 - 01:10:50 CST