Null statement-sequential control, PL-SQL Programming

Assignment Help:

NULL Statement

The NULL statement clearly specifies in action; it does nothing other than to pass control to the next statement. It can, though, improve the readability. In a construct allowing the substitute actions, the NULL statements serve as a placeholder. It tells the readers that the related alternative has not been overlooked, but required that no action is necessary. In the following illustration, the NULL statement shows that no action is taken for the unnamed exceptions:


EXCEPTION
WHEN ZERO_DIVIDE THEN
ROLLBACK;
WHEN VALUE_ERROR THEN
INSERT INTO errors VALUES...
COMMIT;
WHEN OTHERS THEN
NULL;
END;


Each of the clause in an IF statement should contain at least one executable statement. The
NULL statement is executable; therefore you can use it in clauses that correspond to the circumstances in which no action is taken. In the following illustration, the NULL statements emphasize that only top-rated employees get bonus:


IF rating > 90 THEN
compute_bonus(emp_id);
ELSE
NULL;
END IF;


The NULL statement is also a handy way to create stubs when designing the applications from the top down. A stub is dummy subprogram that permits you to defer the definition of a procedure or function till you test and debug the main program. In the following illustration, the NULL statement meets the requirement that at least one statement should appear in the executable part of a subprogram:




PROCEDURE debit_account (acct_id INTEGER, amount REAL) IS
BEGIN
NULL;
END debit_account;


Related Discussions:- Null statement-sequential control

Using raise_application_error - user-defined exceptions, Using raise_applic...

Using raise_application_error The Package DBMS_STANDARD that is supplied with Oracle gives language facilities that help your application to interact with Oracle. For illustra

Renaming columns - sql, Renaming Columns - SQL SQL has no direct count...

Renaming Columns - SQL SQL has no direct counterpart of RENAME. To derive the table on the right in Figure 4.4 from the table on the left, Tutorial D has IS_CALLED RENAME ( St

Parameter and keyword description - loop statements, Parameter and Keyword ...

Parameter and Keyword Description: label_name: This is an undeclared identifier which optionally labels a loop. When used, the label_name should be enclosed by double ang

Miller-urey''s experimental procedure, MILLER-UREY' S EXPERIMENTAL PROCEDU...

MILLER-UREY' S EXPERIMENTAL PROCEDURES - They recreated the probable conditions on the primitive earth in the laboratory. An atmosphere containing hydrogen, ammonia, me

Explicit cursors, Explicit Cursors The set of rows returned by the que...

Explicit Cursors The set of rows returned by the query can include zero, one, or multiple rows, depending on how many rows meet your search criteria. Whenever a query returns

Constants and variables in pl sql, Constants and Variables:   You can...

Constants and Variables:   You can declare the constants and variables in the declarative section of any PL/SQL subprogram, block, or package. The Declarations allot the stor

Procedure, 1. Create a procedure called TAX_COST_SP to accomplish the tax c...

1. Create a procedure called TAX_COST_SP to accomplish the tax calculation task. Keep in mind that the state and subtotal values are inputs into the procedure and the procedure is

In mode - parameter modes, IN Mode An IN parameter pass the values to ...

IN Mode An IN parameter pass the values to the subprogram being called. Within the subprogram, an IN parameter acts like a constant. And hence, it cannot be assigned a value.

Using the collection methods, Using the Collection Methods The collecti...

Using the Collection Methods The collection methods below help to generalize the code and make collections easier to use and also make your applications easier to maintain:

Organic evolution, Organi c Evolution Evolution is a slow continuou...

Organi c Evolution Evolution is a slow continuous, irreversible and natural process of change to give rise to advance and diverse forms of life i.e. formation of new specie

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