Manipulating individual elements - pl/sql, PL-SQL Programming

Assignment Help:

Manipulating Individual Elements

Faraway you have manipulated an entire collection. Within the SQL, to manipulate the individual elements of the collection, and then use the operator TABLE. The operand of TABLE is a subquery which returns a single column value for you to manipulate. That the value is the nested table or the varray.
In the illustration below, you add a row to the History Department nested table stored in the column courses:



BEGIN
INSERT INTO
TABLE(SELECT courses FROM department WHERE name = ’History’)
VALUES(3340, ’Modern China’, 4);
END;


In the next illustration, you revise the number of credits for two courses offered by the Psychology Department:

DECLARE
adjustment INTEGER DEFAULT 1;
BEGIN
UPDATE TABLE(SELECT courses FROM department
WHERE name = ’Psychology’)
SET credits = credits + adjustment
WHERE course_no IN (2200, 3540);
END;

In the following illustration, you retrieve the number and the title of a specific course offered by the History Department:

DECLARE
my_course_no NUMBER(4);
my_title VARCHAR2(35);
BEGIN
SELECT course_no, title INTO my_course_no, my_title
FROM TABLE(SELECT courses FROM department
WHERE name = ’History’)
WHERE course_no = 3105;
...
END;


In the next illustration, you delete all 5-credit courses offered by the English Department:

BEGIN
DELETE TABLE(SELECT courses FROM department
WHERE name = ’English’)
WHERE credits = 5;
END;



In the following illustration, you recover the title and cost of the Maintenance Department’s fourth project from the varray column projects:

DECLARE
my_cost NUMBER(7,2);
my_title VARCHAR2(35);
BEGIN
SELECT cost, title INTO my_cost, my_title
FROM TABLE(SELECT projects FROM department
WHERE dept_id = 50)
WHERE project_no = 4;
...
END;


Presently, you cannot reference the individual elements of a varray in an UPDATE, INSERT, or DELETE statement. And hence, you should use the PL/SQL procedural statements. In the illustration below, the stored procedure add_project inserts a new project into the department’s project list at a given position a shown:

CREATE PROCEDURE add_project (
dept_no IN NUMBER,
new_project IN Project,
position IN NUMBER) AS
my_projects ProjectList;
BEGIN

SELECT projects INTO my_projects FROM department
WHERE dept_no = dept_id FOR UPDATE OF projects;
my_projects.EXTEND; -- make room for new project
/* Move varray elements forward. */
FOR i IN REVERSE position..my_projects.LAST - 1 LOOP
my_projects(i + 1) := my_projects(i);
END LOOP;
my_projects(position) := new_project; -- add new project
UPDATE department SET projects = my_projects
WHERE dept_no = dept_id;
END add_project;

The stored procedure updates below for a given project is:

CREATE PROCEDURE update_project (
dept_no IN NUMBER,
proj_no IN NUMBER,
new_title IN VARCHAR2 DEFAULT NULL,
new_cost IN NUMBER DEFAULT NULL) AS
my_projects ProjectList;
BEGIN
SELECT projects INTO my_projects FROM department
WHERE dept_no = dept_id FOR UPDATE OF projects;
/* Find project, update it, then exit loop immediately. */
FOR i IN my_projects.FIRST..my_projects.LAST LOOP
IF my_projects(i).project_no = proj_no THEN
IF new_title IS NOT NULL THEN
my_projects(i).title := new_title;
END IF;
IF new_cost IS NOT NULL THEN
my_projects(i).cost := new_cost;
END IF;
EXIT;
END IF;
END LOOP;
UPDATE department SET projects = my_projects
WHERE dept_no = dept_id;
END update_project;


Related Discussions:- Manipulating individual elements - pl/sql

Use triggers to maintain referential integrity, At times, Brewbean's has ch...

At times, Brewbean's has changed the id number for existing products. In the past, they have had to add a new product row with the new id to the BB_PRODUCT table, modify all the co

Origin of earth - big bang hypothesis, ORIGIN OF EARTH - BIG-BAN G HY...

ORIGIN OF EARTH - BIG-BAN G HYPOTHESIS - Origin of life is linked to origin of earth. Cosmos, the Universe originated 10-20 billion years ago by Big Bang (thermonu

I want database development with analysis tools, Project Description: I ...

Project Description: I want a database for large governmental and private data sets on one country that will be easily extended to other countries in the future. Also, the datab

Overloading, Overloading The PL/SQL overloads the subprogram names. T...

Overloading The PL/SQL overloads the subprogram names. That is, you can use similar name for few different subprograms as long as their formal parameters differ in the number

Biconditional - sql, Biconditional - SQL The biconditional p ↔ q can b...

Biconditional - SQL The biconditional p ↔ q can be expressed in Tutorial D by p = q and the same is true of SQL. The question then arises as to whether, in SQL, p = q is equiv

Aggregate operators sql, Aggregate Operators SQL Supports all of the a...

Aggregate Operators SQL Supports all of the aggregate operators mentioned in the theory book and many more besides. The syntax, however, involves an unusual trick that SQL cal

Using aliases-declarations in sql, Using Aliases The Select-list items f...

Using Aliases The Select-list items fetched from a cursor related with the %ROWTYPE should have simple names or, if they are expressions, should have aliases. In the example bel

How pl/sql resolves the calls? , How Calls Are Resolved? The figure sho...

How Calls Are Resolved? The figure shows that how the PL/SQL compiler resolves the subprogram calls. When the compiler encounters the procedure or function call, it tries to di

Parameter and keyword description - exit statement, Parameter and Keyword D...

Parameter and Keyword Description: EXIT: An unconditional EXIT statement (i.e., one without a WHEN clause) exits the present loop instantly. The Execution resumes with th

Oracle 10g new features and differences , Oracle 10G new features:- Au...

Oracle 10G new features:- Automatic Database Diagnostic Monitor System Advancements - these methods will provides several methods for extracting reports through the Automatic

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