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 delete - collection method, Using DELETE This process has three ...

Using DELETE This process has three forms. The DELETE removes all elements from the collection. DELETE(n) removes the nth element from the nested table. When n is null, then D

Differentiate between snowflake schema and star schema, Problem: (a) De...

Problem: (a) Define the following terms: (i) data mining. (ii) OLAP. (b) Differentiate between snowflake schema and star schema. Support your answer with appropriate

Package standard in pl/sql, Package STANDARD package named STANDARD d...

Package STANDARD package named STANDARD defines the PL/SQL atmosphere. The package specification globally declares the exceptions, types, and subprograms that are available a

Opening a cursor variable, Opening a Cursor Variable The OPEN-FOR stat...

Opening a Cursor Variable The OPEN-FOR statement relates a cursor variable with the multi-row query, executes the query, and then identifies the result set. The syntax for ope

Declaring a cursor, Declaring a Cursor The Forward references are not ...

Declaring a Cursor The Forward references are not allowed in the PL/SQL. Therefore, you must declare a cursor before referencing it in other statements. Whenever you declare a

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

Data types in sql, Data Types in SQL SQL's concept does not differ sig...

Data Types in SQL SQL's concept does not differ significantly from that defined in the theory book, apart from that business concerning NULL. However, the theory book equates

Example of check constraints - sql, Example of Check Constraints Examp...

Example of Check Constraints Example: Workaround for when subqueries not permitted in CHECK constraints CREATE FUNCTION NO_MORE_THAN_20000_ENROLMENTS ( ) RETURNS BOOLEAN

%rowcount - implicit cursor attributes, %ROWCOUNT The %ROWCOUNT yields...

%ROWCOUNT The %ROWCOUNT yields the number of rows affected by the INSERT, UPDATE, or DELETE statement, or returned by a SELECT INTO statement. The %ROWCOUNT yields zero when a

Parameter and keyword description - %type attribute, Parameter and Keyword ...

Parameter and Keyword Description: collection_name: This keyword identifies the index-by table, nested table, or varray formerly declared within the present scope. cu

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