Using extend - collection method, PL-SQL Programming

Assignment Help:

Using EXTEND

To enlarge the size of a collection, use EXTEND. This process has 3 forms. The EXTEND appends one null element to a collection. And the EXTEND(n) appends n null elements to a collection. EXTEND(n,i) appends n copies of the ith element to the  collection. For e.g. the statement below appends 5 copies of element 1 to nested table courses:

courses.EXTEND(5,1);

You cannot use the EXTEND to initialize an automatically null collection. In addition if you impose the NOT NULL constraint on a TABLE or VARRAY type, you cannot apply the first two forms of EXTEND to collections of that kind.

The EXTEND operates on the internal size of the collection, that includes any deleted elements. Therefore, if EXTEND encounters deleted the elements, then it includes them in its tally. The PL/SQL keeps placeholders for the deleted elements so that you can swap them whenever you wish. Consider the example shown below:

DECLARE

TYPE CourseList IS TABLE OF VARCHAR2(10);

courses CourseList;

BEGIN

courses := CourseList('Biol 4412', 'Psyc 3112', 'Anth 3001');

courses.DELETE(3); -- delete element 3

/* PL/SQL keeps a placeholder for element 3. So, the

next statement appends element 4, not element 3. */

courses.EXTEND; -- append one null element

/* Now element 4 exists, so the next statement does

not raise SUBSCRIPT_BEYOND_COUNT. */

courses(4) := 'Engl 2005';

Whenever it includes deleted elements, then the internal size of a nested table differs from the values returned by the COUNT and LAST. For illustration, when you initialize a nested table with five elements, delete the elements 2 & 5, then the internal size is 5, and the COUNT returns 3, &  the LAST returns 4. All the deleted elements are treated similarly.


Related Discussions:- Using extend - collection method

Insert command in sql, INSERT Command in SQL Loosely speaking, INSERT...

INSERT Command in SQL Loosely speaking, INSERT takes the rows of a given source table and adds them to the specified target table, retaining all the existing rows in the targ

Updating by insertion, Updating by insertion Syntax : INSERT IN...

Updating by insertion Syntax : INSERT INTO ENROLMENT VALUES (SID ('S4'), 'Devinder', CID ('C1'));

Effect of anonymous columns, Effect of Anonymous Columns Now, recall t...

Effect of Anonymous Columns Now, recall that a VALUES expression denotes a table with undefined column names. If an initial value is to be specified when a base table is creat

Package specification, The Package Specification The package specificat...

The Package Specification The package specifications contain the public declarations. The scopes of these declarations are local to your database representation and global to t

%found - implicit cursor attributes, %FOUND Until the SQL data manipul...

%FOUND Until the SQL data manipulation statement is executed, the %FOUND yields NULL. Afterward, the %FOUND yields TRUE, when an INSERT, UPDATE, or DELETE statement affected o

Parameter aliasing, Parameter Aliasing   To optimize the subprogram ca...

Parameter Aliasing   To optimize the subprogram call, the PL/SQL compiler can decide between the two techniques of the parameter passing. With the by-value techniques, the v

Selecting objects in pl sql, Selecting Objects: Suppose that you have ...

Selecting Objects: Suppose that you have run the SQL*Plus script below that creates object type Person and object table persons, and that you have settled the table: CREATE

Close statement in pl sql, CLOSE Statement The CLOSE statement allows ...

CLOSE Statement The CLOSE statement allows the resources held by a cursor variable or open cursor to be reused. No more rows can be fetched from the cursor variable or closed

Advantages of exceptions, Advantages of Exceptions Using the exception...

Advantages of Exceptions Using the exceptions for the error handling has many benefits. Without an exception handling, every time you issue a command, you should ensure for th

Develop a job management site, Lightweight system to provide and take info ...

Lightweight system to provide and take info from workers in the field and office, have basic design outlined already just require build and implementation Desired Skills CSS,

Write Your Message!

Captcha
Free Assignment Quote

Assured A++ Grade

Get guaranteed satisfaction & time on delivery in every assignment order you paid with us! We ensure premium quality solution document along with free turntin report!

All rights reserved! Copyrights ©2019-2020 ExpertsMind IT Educational Pvt Ltd