Sequences in Oracle

What is a sequence?

A sequence is a database object used to generate a unique, contiguous integer. A sequence is typically used to automatically generate a value for a primary key or unique key. Sequences can be in ascending order or in descending order.

In fact, the sequence in Oracle is almost a meaning of self-growth in MySQL.

Create a sequence

Creates a sequence. Starting from the sequence Number 10, increase each time 1, the maximum is 2000, do not cycle, and then increase the error

CREATE SEQUENCE seq1
START with 10
INCREMENT by 1
MAXVALUE 2000
Nocycle
CACHE 30;

Access sequence

Access Next:

Seq1. Nextval

Query current:

SELECT seq1. Currval from dual;

Change sequence

ALTER SEQUENCE seq1
MAXVALUE 5000--Max 5000
CYCLE; --Cycle

Delete a sequence

DROP SEQUENCE seq1;

Using the Sys_guid function

SELECT Sys_guid () from dual;

Sequences in Oracle