Kinder garden question about datatype

[joozh]

Hi all,

Suppose I know that the maximum length for my customerID field will not be more than 10 characters (95% of times this will be numeric digits like 1000127, while 5% of the times this may be alphanumeric like 1001MT56).

Given this scenario should I use char(10) as the datatype for my customerID field or should I use varchar(10). Can you kindly share your expert advise from a performance aspect.

BOL has a lot of information but I could not the exact answer to this "kiddy" questions and thus ended up posting this question here.

[rmiao]

I'll use char(10) in this case since varchar type will add 2 bytes overhead and sql has to recalculate length every time you update the value in the column.