sequences的用法

CREATE SEQUENCE supplier_seq

MINVALUE 1

MAXVALUE 999999999999999999999999999

START WITH 1

INCREMENT BY 1

CACHE 20;

This would create a sequence object called supplier_seq. The first sequence number that it would use is 1 and each subsequent number would increment by 1 (ie: 2,3,4,...}. It will cache up to 20 values for performance.

Now that you've created a sequence object to simulate an autonumber field, we'll cover how to retrieve a value from this sequence object. To retrieve the next value in the sequence order, you need to use nextval.

For example:

supplier_seq.nextval

This would retrieve the next value from supplier_seq. The nextval statement needs to be used in an SQL statement. For example:

INSERT INTO suppliers

(supplier_id, supplier_name)

VALUES

(supplier_seq.nextval, 'Kraft Foods');