Go Up to Working with Generators
A generator is a mechanism that creates a unique, sequential number that is automatically inserted into a column in a read-write database when SQL data manipulation operations such as
UPDATE occur. Generators are typically used to produce unique values that can be inserted into a column that is used as a
PRIMARY KEY. For example, a programmer writing an application to log and track invoices may want to ensure that each invoice number entered into the database is unique. The programmer can use a generator to create the invoice numbers automatically, rather than writing specific application code to accomplish this task.
Any number of generators can be defined for a database, as long as each generator has a unique name. A generator is global to the database where it is declared. Any transaction that activates the generator can use or update the current sequence number. InterBase will not assign duplicate generator values across transactions.