Creating and Using Type in Oracle Database

Oracle Database allows developers to create their own datatypes and use them in column of database tables. These user-defined datatypes are called as 'Type'.


Creating a Type

Syntax:
CREATE TYPE <TYPE_NAME> AS OBJECT
(<COLUMN_NAME> <DATATYPE>(<SIZE>),
... N);
Example:
CREATE TYPE MYADDRESS AS OBJECT
(PLOT NUMBER (4),
CITY VARCHAR2 (10),
COUNTRY VARCHAR2 (10),
PIN NUMBER (6));

Above example will create a user-defined type called 'MYADDRESS'.

Note: To display the structure of a type, we can use the DESC command.


Using a Type in a Table

The example below shows how to use a type while creating a table in Oracle database.

CREATE TABLE EMP
(EMPNO NUMBER(4),
NAME VARCHAR2(10),
SAL NUMBER(7, 2),
ADDRESS MYADDRESS);

Inserting Data into a User-Defined Type Column

The example below shows how to insert data into a column having user-defined type.

INSERT INTO EMP(
VALUES(1, 'ARNOLD', 5000, 
       MYADDRESS(100, 'SYDNEY', 'AUSTRALIA', 17200));

Selecting Data from a User-Defined Type Column

The example below shows how to select data from a user-defined type column.

SELECT ENAME, E.EMPNO, E.ADDRESS.PLOT,
E.ADDRESS.CITY, E.ADDRESS.COUNTRY, E.ADDRESS.PIN,
FROM EMP;

Note: Table alias must be used to extract data from user defined type column.


Deleting a Type

We can use the DROP statement to delete a type as shown below:

DROP TYPE MYADDRESS;

Note: Types having table dependency cannot be deleted i.e. if a type is associated with a table it cannot be deleted. In order to delete a type the dependency should first be removed.

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