BigInt or Varchar for a large number I won't ever sort / calculate on I need to store users' Facebook IDs in a column in my DB. 

The ID always consists of only digits, and can be as large as a number in excess of 500 million. Considering that I won't ever need to do any arithmetic, sorting or use relational operators on the values, what would be a better choice: BigInt or varchar ? 

The value will always be unique and never non-existent (null)

The only operation I do is check for the existence of an ID in the database, i.e. the = operator.
varchar adds overhead:


length of the string needs stored (extra 2 bytes IIRC in MySQL) per field and in the index
requires more processing for collation on comparison


Saying that, what does the Facebook API describe the type as? Use the "native" one of course