Row_number() function in sql server is used to generate a serial number for a given record set. But we need to use ORDER BY clause so that the numbers are assigned to the specific order.

CREATE TABLE #TEMP (NAMES VARCHAR(100))
INSERT INTO #TEMP
SELECT 'Hitesh' UNION ALL
SELECT 'Abhimanyu' UNION ALL
SELECT 'Priyanka' UNION ALL
SELECT 'Dev' UNION ALL
SELECT 'Bhawesh'

SELECT NAMES,ROW_NUMBER() OVER (ORDER BY NAMES) AS SNO FROM #TEMP

drop table #TEMP

Result :

Row_Number