------------------- Sequence generators ------------------- Function: A sequence generator is a mechanism for generating successive exact numeric values, one at a time. A sequence generator is a named schema object. Syntax rules: CREATE { SEQUENCE | GENERATOR } <name> DROP { SEQUENCE | GENERATOR } <name> SET GENERATOR <name> TO <start_value> ALTER SEQUENCE <name> RESTART WITH <start_value> GEN_ID (<name>, <increment_value>) NEXT VALUE FOR <name> Type: INTEGER in dialect 1, BIGINT in dialect 3 Example(s): 1. CREATE SEQUENCE S_EMPLOYEE; 2. ALTER SEQUENCE S_EMPLOYEE RESTART WITH 0; 3. SELECT GEN_ID(S_EMPLOYEE, 1) FROM RDB$DATABASE; 4. INSERT INTO EMPLOYEE (ID, NAME) VALUES (NEXT VALUE FOR S_EMPLOYEE, 'John Smith'); Note(s): 1. SEQUENCE is a syntax term declared in the SQL specification, while GENERATOR is a legacy InterBase syntax term. It's recommended to use the standard SEQUENCE syntax in your applications. 2. Currently, increment values not equal to 1 (one) could be used only via the GEN_ID function. The future versions are expected to provide full support for SQL-99 sequence generators (which allows the required increment values to be specified at the DDL level), so it's recommended to get new sequential values via NEXT VALUE FOR value expression instead of the GEN_ID function, unless it's vitally important to use other increment values. 3. GEN_ID(<name>, 0) allows you to retrieve the current sequence value, but it should be never used in insert/update statements, as it produces a high risk of uniqueness violations in a concurrent environment.