1/28/16

OBJECT VIEWS AND METHODS

OBJECT VIEWS


If you want to implement objects with the existing table, object views come into picture.

You define the object and create a view which relates this object to the existing table nothing but object view.

Object views are used to relate the user defined objects to the existing table.


Ex:

1)  Assume that the table student has already been created with the following columns SQL> create table student(no number(2),name varchar(10),hno number(3),city

varchar(10));

2)  Create the following types

SQL> create type addr as object(hno number(2),city varchar(10));/ SQL> create type stud as object(name varchar(10),address addr);/ 3) Relate the objects to the student table by creating the object view

SQL> create view student_ov(no,stud_info) as select no,stud(name,addr(hno,city)) from student;
4)  Now you can insert data into student table in two ways

a)  By regular insert

SQL> Insert into student values(1,’sudha’,111,’hyd’); b) By using object view
SQL> Insert into student_ov values(1,stud(‘sudha’,addr(111,’hyd’)));

METHODS


You can define methods which are nothing but functions in types and apply in the tables which holds the types;

Ex:

1) Defining methods in types

SQL> Create type stud as object(name varchar(10),marks number(3), Member function makrs_f(marks in number) return number,





Pragma restrict_references(marks_f,wnds,rnds,wnps,fnps));/ 2) Defining type body
SQL> Create type body stud as

Member function marks_f(marks in number) return number is Begin

Return (marks+100); End marks_f;

End;/

3) Create a table using stud type

SQL> Create table student(no number(2),info stud); 4) Insert some data into student table
SQL> Insert into student values(1,stud(‘sudha’,100)); 5) Using method in select
SQL> Select s.info.marks_f(s.info.marks) from student s;


-- Here we are using the pragma restrict_references to avoid the writes to the database.




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