Keeping Code Consistent with User-Defined Subtypes : Subtype Custom Type « PL SQL Data Types « Oracle PL/SQL Tutorial

1. Oracle PL/SQL Tutorial
2. PL SQL Data Types
3. Subtype Custom Type

declare
  subtype newSubtype is standardType [NOT NULL];

You can create subtypes in the declaration portions of procedures, functions, anonymous blocks, packages, or package bodies.

create or replace package pkg_global
 is
      subtype large_string  is VARCHAR2(2000);
      subtype medium_string is VARCHAR2(256);
      subtype small_string  is VARCHAR2(10);
      subtype flag_yn       is VARCHAR2(1) not null;
 end;
 /

Referencing Subtypes

SQL>
SQL> declare
  2      v_medium_tx pkg_global.medium_string;
  3      v_small_tx  pkg_global.small_string := 'ABC';
  4      v_flag_yn   pkg_global.flag_yn :='N';
  5  begin
  6     v_medium_tx:=v_small_tx||'-'||v_flag_yn;
  7  end;
  8  /

PL/SQL procedure successfully completed.

SQL>
SQL>