The amount of memory will depend solely on the data you store in this case. You won't use any more memory declaring the column number(4,0)
, you won't save any declaring the column number(2,0)
. You can use the vsize
function to see the actual amount of space required to store any particular piece of information. In this case, you'll need 2 bytes for each number regardless of the data type which you can see in this SQL Fiddle.
Of course, if you declare the column number(4,0)
, you should assume that someone will store values larger than 99 in that table so you'd need to ensure that your code can handle that appropriately.