The number assigned to an employee, customer, vendor or product for identification. Although it may contain only numeric digits, account numbers are often defined and stored as a character field, also known as a "string" or "alphanumeric field," so that parts of the number can be searched independently.

For example, if the first two digits in a customer number were a state code, and the next three were the city code, state and city could be easily searched. Take the case of searching for state code "44" and city code "111" on a 14-digit account number defined as the following three subfields:

   Subfield     Positions in Field

   State Code    1-2
   City Code     3-5
   Customer #    6-14

If the field were defined as characters (a string), the query would be LOOK FOR "44111" IN CHARACTERS 1-5. If the field were defined as a numeric field, the entire number has to be taken into consideration, making it awkward. The query would have to be GREATER THAN 44110999999999 AND LESS THAN 44112000000000. See string.