Execute the following Microsoft SQL Server Transact-SQL demonstration scripts in Management Studio Query Editor.

USE AdventureWorks;

SELECT TotalSickHours=sum(SickLeaveHours),

       AverageSickHours=avg(SickLeaveHours)

FROM HumanResources.Employee

     TABLESAMPLE SYSTEM (3 * 5 PERCENT);

/*  TotalSickHours      AverageSickHours

            1797              47  */

Related article:

Limiting Result Sets by Using TABLESAMPLE