group by and row no in sql

SELECT ROW_NUMBER()  OVER (ORDER BY  ColumnName1) As SrNo, ColumnName1,  ColumnName2 FROM  TableName

SELECT DENSE_RANK()  OVER (ORDER BY  ColumnName1) As SrNo, ColumnName1,  ColumnName2 FROM  TableName

select top 1 ROW_NUMBER()over(orderby col1)as slno,* from tbl1 orderby slno desc