How to get data in that form using SQL Query

Question

I have stored data in one table 't' in which I have all year data of user what I have . In result of query I want the total number of new users as per year.

Example:

year , count
1991   360
1992   640
2000   2000

Result required:

Year, NewUsers
1991  360
1992  280 (640-360)
2000  1720

Answer 1

You could define a variable to do this:

select
    `year`,
    @lastval := `count` - @lastval as newusers
from yourtable
cross join (select @lastval := 0) a
order by `year`

See demo in SQLFiddle.