What Is Enum Data Type in Oracle?
In Oracle, the ENUM data type is not natively supported. However, you can simulate an enumeration-like behavior using a combination of check constraints and user-defined types. This allows you to define a predefined set of values that a column can store.
Creating an Enum-Like Data Type
To create an enum-like data type in Oracle, you need to follow these steps:
- Create a new object type using the CREATE TYPE statement.
- Add the desired values as attributes to the object type.
- Create a table with a column of the newly created object type.
- Add a check constraint to enforce the predefined values for the column.
Let’s walk through an example to understand this better:
Step 1: Create Object Type
To create an object type, you can use the following syntax:
CREATE TYPE enum_type AS OBJECT ( value VARCHAR2(20) );
The above code creates an object type called enum_type. It has a single attribute called value, which will store the allowed values for our enum-like data type.
Step 2: Add Values as Attributes
In this step, we will add our desired values as attributes to the object type. For example, let’s say we want our enum-like data type to have three possible values: ‘ACTIVE’, ‘INACTIVE’, and ‘PENDING’.
ALTER TYPE enum_type ADD ATTRIBUTE ( ACTIVE VARCHAR2(20), INACTIVE VARCHAR2(20), PENDING VARCHAR2(20) );
The above code adds the attributes ACTIVE, INACTIVE, and PENDING to the enum_type.
Step 3: Create Table with Enum-Like Column
In this step, we will create a table that has a column of our newly created enum-like data type.
CREATE TABLE my_table ( status enum_type );
The above code creates a table called my_table. It has a single column called status, which is of type enum_type.
Step 4: Add Check Constraint for Valid Values
To enforce the predefined values for the column, we need to add a check constraint.
ALTER TABLE my_table ADD CONSTRAINT valid_status_values CHECK (status.value IN ('ACTIVE', 'INACTIVE', 'PENDING'));
The above code adds a check constraint called valid_status_values. It ensures that only the allowed values (‘ACTIVE’, ‘INACTIVE’, and ‘PENDING’) can be inserted into the status column of the my_table.
In Oracle, although there is no direct support for ENUM data type, you can simulate its behavior using user-defined types and check constraints. By following the steps outlined in this tutorial, you can create enum-like data types and ensure that only the predefined values are stored in the corresponding columns.
Remember: Enum-like data types can provide clarity and maintainability to your database schema by restricting the possible values for specific columns.
Now that you understand how to create an enum-like data type in Oracle, you can apply this knowledge to structure your database schema more effectively!