Jul 18, 2016 But, Oracle does not have an AUTOINCREMENT feature. How can you do it in Oracle? How To Create an Auto Increment Column in Oracle 11g. If you’re using Oracle 11g or earlier, you create it in a different way than if you are using Oracle 12c. To create an auto incrementing column in Oracle 11g, you can follow these steps: Create a sequence. TopLink may create entity identifiers (or primary keys) automatically using any of the following strategies defined by JPA. By specifying a strategy of AUTO you are indicating your intention to let TopLink pick the strategy to use. Typically, TopLink picks TABLE as the strategy, since it is the most portable strategy available (it does not.
This Oracle tutorial explains how to create, drop, disable, and enable a primary key in Oracle with syntax and examples.
What is a primary key in Oracle?
In Oracle, a primary key is a single field or combination of fields that uniquely defines a record. None of the fields that are part of the primary key can contain a null value. A table can have only one primary key.
Note
- In Oracle, a primary key can not contain more than 32 columns.
- A primary key can be defined in either a CREATE TABLE statement or an ALTER TABLE statement.
Oracle Auto Generate Primary Key Sql
Create Primary Key - Using CREATE TABLE statement
You can create a primary key in Oracle with the CREATE TABLE statement.
Syntax
The syntax to create a primary key using the CREATE TABLE statement in Oracle/PLSQL is:
Example
Let's look at an example of how to create a primary key using the CREATE TABLE statement in Oracle:
In this example, we've created a primary key on the supplier table called supplier_pk. It consists of only one field - the supplier_id field.
We could also create a primary key with more than one field as in the example below:
Create Primary Key - Using ALTER TABLE statement
You can create a primary key in Oracle with the ALTER TABLE statement.
Syntax
The syntax to create a primary key using the ALTER TABLE statement in Oracle/PLSQL is:
Example
Let's look at an example of how to create a primary key using the ALTER TABLE statement in Oracle.
In this example, we've created a primary key on the existing supplier table called supplier_pk. It consists of the field called supplier_id.
We could also create a primary key with more than one field as in the example below:
Drop Primary Key
You can drop a primary key in Oracle using the ALTER TABLE statement.
Syntax
The syntax to drop a primary key using the ALTER TABLE statement in Oracle/PLSQL is:
Example
Let's look at an example of how to drop a primary key using the ALTER TABLE statement in Oracle.
In this example, we're dropping a primary key on the supplier table called supplier_pk.
Disable Primary Key
You can disable a primary key in Oracle using the ALTER TABLE statement.
Oracle Auto Generate Primary Key Name
Syntax
The syntax to disable a primary key using the ALTER TABLE statement in Oracle/PLSQL is:
Example
Let's look at an example of how to disable a primary using the ALTER TABLE statement in Oracle.
In this example, we're disabling a primary key on the supplier table called supplier_pk.
Oracle Auto Generate Primary Keys
Enable Primary Key
You can enable a primary key in Oracle using the ALTER TABLE statement.
Syntax
The syntax to enable a primary key using the ALTER TABLE statement in Oracle/PLSQL is:
Example
Oracle Auto Generate Primary Key Examples
Let's look at an example of how to enable a primary key using the ALTER TABLE statement in Oracle.
In this example, we're enabling a primary key on the supplier table called supplier_pk.
Similar to MySQL, PostgreSQL, Oracle, and many other relational databases, SQL Server is best utilized when assigning unique primary keys to most database tables.
The advantages to using numeric, auto incremented primary keys are numerous, but the most impactful benefits are faster speed when performing queries and data-independence when searching through thousands of records which might contain frequently altered data elsewhere in the table. With a consistent and unique numeric identifier, applications can take advantage of these faster and more reliable queries.
Basic Table Creation
Once connected to your SQL Server, you’d normally start by
CREATING
a new table that contains the the field you wish to use as your incremented primary key. For our example, we’ll stick with the tried and true id
field:The problem here is, we have no way of controlling our
id
field. When a new record is inserted, we not only must manually enter a value for id
, but we have to perform a query ahead of time to attempt to verify that id
value doesn’t already exist (a near-impossibility when dealing with many simultaneous connections).Using Identity and Primary Key Constraints
The solution turns out to be using two constraint options provided by SQL Server.
The first is
PRIMARY KEY
, which as the name suggests, forces the specified column to behave as a completely unique index for the table, allowing for rapid searching and queries.While SQL Server only allows one
PRIMARY KEY
constraint assigned to a single table, that PRIMARY KEY
can be defined for more than one column. In a multi-column scenario, individual columns can contain duplicate, non-unique values, but the PRIMARY KEY
constraint ensures that every combination of constrained values will in fact be unique relative to every other combination.The second piece of the puzzle is the
IDENTITY
constraint, which informs SQL Server to auto increment the numeric value within the specified column anytime a new record is INSERTED
. While IDENTITY
can accept two arguments of the numeric seed
where the values will begin from as well as the increment
, these values are typically not specified with the IDENTITY
constraint and instead are left as defaults (both default to 1
).With this new knowledge at our fingertips, we can rewrite our previous
CREATE TABLE
statement by adding our two new constraints.That’s all there is to it. Now the
id
column of our books
table will be automatically incremented upon every INSERT
and the id
field is guaranteed to be a unique value as well.