Introduced in SQL Server 2005, TABLESAMPLE allows you to extract
a sampling of rows from a table in the FROM clause. The rows
retrieved are random and they are are not in any order. This
sampling can be based on a percentage of number of rows. You can
use TABLESAMPLE when only a sampling of rows is necessary for
the application instead of a full result set. TABLESAMPLE SYSTEM
(10 PERCENT) TABLESAMPLE SYSTEM (1000 ROWS) If you run above
script many times you will notice that different numbers of rows
are returned everytime. Without any data changing, re-running
the identical query keeps giving different results. This is non
-deterministic factor of TABLESAMEPLE clause. If table is static
and rows are not changed what could be the reason to return
different numbers of the rows to return in each execution. The
factor is 10 PERCENT is not the percentages of the table rows or
tables records, it is percentages of the table’s data pages.
Once the sample pages of data selected, all the rows from the
selected pages ar