This is a common confusion ... BIGINT
type has a fixed size is stored on 8B so the ONLY difference between BIGINT(1)
and BIGINT(20
) is the number of digits that is gonna be displayed 1 digit respectively 20 digits .
If you store only 3 digits numbers ,and you do not think you will need more you can use a SMALLINT UNSIGNED
type which takes only 2B instead of 8B so you will save a lot of space and the performance will increase.
I suggest you read this first.