PL/SQL自定义子类型实例讲解

SUBTYPE CHARACTER IS CHAR; 
SUBTYPE INTEGER IS NUMBER(38,0);

DECLARE 
   SUBTYPE name IS char(20); 
   SUBTYPE message IS varchar2(100); 
   salutation name; 
   greetings message; 
BEGIN 
   salutation := 'Reader '; 
   greetings := 'Welcome to the World of PL/SQL'; 
   dbms_output.put_line('Hello ' || salutation || greetings); 
END; 

输出结果：
Hello Reader              Welcome to the World of PL/SQL