User-defined subtypes

In PL/SQL, you can define a user-defined subtype based on a base data type using the SUBTYPE statement. You can also define a user-defined subtype based on another user-defined type.

The syntax for defining a user-defined subtype SUBTYPE is as follows:

SUBTYPE subtype_name IS base_type
{ precision [, scale ]  [ NOT NULL ]

For user-defined types, you can redefine the precision or add a NOT NULL constraint. Here is an example:

obclient> DECLARE
  SUBTYPE score IS NUMBER;
  amount score(6,2);

  SUBTYPE item IS score NOT NULL;
  item1 item := 1;

BEGIN
  amount := item1;
END;
/