AutoNumber is a type of data used in Microsoft Access tables to generate an automatically incremented numeric counter. It may be used to create an identity column which uniquely identifies each record in a table. Only one AutoNumber field is allowed in each table which called Counter in Access. The default AutoNumber type is a start + increment counter and start value of 1 and an increment of 1. Although in many instances such an AutoNumber field will appear as if it contains the row count, it does not. Deletion of rows from a table, for example, does not cause AutoNumber fields to be renumbered, but instead leaves holes in the numbering. Similarly, if a transaction to add a row to a table is begun but later aborted, the AutoNumber assigned for that row will not be re-used. There are reasons to choose each form, and trade-offs in doing so. The default start and increment values might reveal information about a table that it is desired not to reveal to people viewing individual table rows. For example, using an AutoNumber field for a customer ID might reveal information that it is desirable not to reveal to, say, customer number 6. T