Sequences in Oracle SQL

What is Sequence?

We create a sequence to generate a unique numbers.

How to Create sequences

We create a sequence by using CREATE SEQUENCE statement

For example:

Create sequence for the EMPNO column of the EMP table begins the sequence at 1 and maximum value at 1000.

CREATE SEQUENCE NEWEMP_EMPNO

INCREMENT BY 1

START WITH 1

MAXVALUE 1000;

=>Explanation of Above Query:

The INCREMENT BY option specifies the gap between sequence numbers

START WITH option specifies the first number in the sequence.

MAXVALUE option specifies the maximum value the sequence can generate.

=>Other option not included in example

NOMAXVALUE: a default maximum value

NOMAINVALUE: specific the minimum sequence value.

CYCLE: cycle option specifies that the sequence continues to generate values.

CACHE: specifies the number of values the server reallocates in memory

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