How to add a sequence to an Oracle table column

Oracle Database Tips by Donald BurlesonAugust 8, 2015

Question: I have a table that needs a sequence as the primary key and I need to know how to add the sequence to the Oracle table column. How do I add a sequence to an Oracle table column?

Answer: Depending on your release a sequence many or may not be associated directly with your table column. For example, in all releases of Oracle, as sequence is associated with a table column only at insert time. As we see below, the table does not "know" that a sequence has been defined for the column, the developer must know the sequence name and use it at table rows insert time:

create sequence my_test_id_seq increment by 1;

create table
   my_test
(
   id   integer,
    name varchar(10)
);

insert into
   my_test
(id,name)
values
(
   my_test_id_seq.nextval,
   'Donnie');

Tip! In order to loosely associate a sequence with a table column you can make the sequence the same name as the table and data column name, suffixed with "_seq". For example, a sequence on a customer table's cust_id_column could be "customer_cust_id_seq". That way, you can find the sequences for the table column in the dba_sequences view.

In Oracle 12c and beyond, you can associate a sequence directly with a table: In this example, we associate the sequence with the table, directly in the create table statement.

create sequence my_test_id_seq increment by 1;

create table
   my_test
(
id        number default my_test_id_seq.nextval,
name      varchar(10)
);

insert into
   my_test
(name)
values
   ('no sequence required!');

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