select name from table;

Jay 1
roy 2
ravi 3
ram 4

select name,
      @rownum := @rownum + 1 as row_number
from your_table
cross join (select @rownum := 0) r
order by name

cross join (select @rownum := 0) r

set @rownum := 0;

select name,
      @rownum := @rownum + 1 as row_number
from your_table
order by name;

SELECT
    name,
    ROW_NUMBER() OVER ()
FROM table

Jay  1
roy  2
ravi 3
ram  4

SELECT
    name,
    ROW_NUMBER() OVER (ORDER BY name DESC)
FROM table
ORDER BY name

Jay  4
ram  3
ravi 2
roy  1