The size of a composite key is computed by adding the key sizes of all fields. For example, if you generate a composite key by combining the Person_Name and Address_part1 fields that have 8 bytes each, the size of the composite key is 16 bytes. If you generate a composite key with the Person_Name and Telephone_Number fields that have 8 and 16 bytes respectively, the size of the composite key is 24 bytes.