What is a sequence in oracle database?

A sequence is an object in oracle database i.e used to generate a number sequence. This can be useful when you need to create a unique number that acts as the primary key.

E.g:-

Create Sequence SEQ_TEST

MinValue 1

MaxValue 999999999

Increment by 1

Start With 1

NoCache NoOrder NoCycle;

Note:- Here SEQ_TEST is the name of the sequence, then after we need to set the parameter according to our conditions and requirements.

Call the Sequence in select statement:-

Query:- select SEQ_TEST1.nextval from dual;

Check the list of sequences created in database user:

Query:- Select  * from User_Sequences;

Conditions:-
* When we have a requirement to change the sequence increment number from 1 to increment by 5 then

Query:-  Alter Sequence SEQ_TEST increment by 5;

*When we a condition to restart the sequence then
Query:-  Alter Sequence SEQ_TEST Restart With 1;

* In this sequence code we have set NoCache, Suppose we have set Cache 5 then it will store the upcoming 5 number in the memory and the LAST_NUMBER of the sequence as per the cache i.e +5 it will update automatically.

Query to update or change the cache value in sequence:-
Alter Sequence SEQ_TEST Cache 5; ----> (Here it will set the cache 5 in your sequence)