While-loop - iterative control, PL-SQL Programming

Assignment Help:

WHILE-LOOP

The WHILE-LOOP statement relates a condition with the series of statements enclosed by the keywords LOOP and END LOOP, as shown:

WHILE condition LOOP
sequence_of_statements
END LOOP;

Before each of the iteration of the loop, the condition is computed. If the condition is true, then the series of statements is executed, then the control resumes at the top of the loop. When the condition is false or null, the loop is then bypassed and control passes to the next statement. An illustration is shown below:

WHILE total <= 25000 LOOP
...
SELECT sal INTO salary FROM emp WHERE...
total := total + salary;
END LOOP;

The number of iterations depends on the condition and is not known until the loop done. The condition is tested at the top of the loop, so the series might execute zero times. In the last illustration, if the initial value of total is bigger than 25000, the condition is false and the loop is bypassed.

A few languages have a LOOP UNTIL or REPEAT UNTIL structure, that tests the condition at the bottom of the loop rather than at the top. So, the sequence of the statements is executed at least once. The PL/SQL has no such structure, but you can easily build one, as shown:

LOOP
sequence_of_statements
EXIT WHEN boolean_expression;
END LOOP;

To make sure that a WHILE loop executes at least once, then use an initialized Boolean variable in the condition which is as shown below:

done := FALSE;
WHILE NOT done LOOP
sequence_of_statements
done := boolean_expression;
END LOOP;


The statement inside the loop should assign a new value to the Boolean variable. Or else, you have an infinite loop. For illustration, the following LOOP statements are logically equal:

WHILE TRUE LOOP | LOOP
... | ...
END LOOP; | END LOOP;


Related Discussions:- While-loop - iterative control

Goto statement - sequential control, GOTO Statement The GOTO statement b...

GOTO Statement The GOTO statement branches to a label unconditionally. The label must be exclusive within its scope and should precede an executable statement or a PL/SQL block.

Delete statement - syntax, DELETE Statement The DELETE statement elimin...

DELETE Statement The DELETE statement eliminates whole rows of data from the specified table or view. Syntax:

Object type in pl/sql, Object Type: The object type is a user-define...

Object Type: The object type is a user-defined composite datatype which encapsulates a data structure along with the functions and procedures required to manipulate the data

Package standard, Package STANDARD The package named STANDARD defines t...

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

Keys in sql, Keys in SQL SQL support for keys in the following respect...

Keys in SQL SQL support for keys in the following respects: SQL does not require at least one key for every base table. If no key is explicitly declared, then KEY {ALL B

Database values-assignments in pl/sql, Database Values You can use the S...

Database Values You can use the SELECT statement to have the Oracle assign values to a variable. For Each and every item in the select list, there must be a matching, type-compa

Avoiding collection exceptions, Avoiding Collection Exceptions   In ma...

Avoiding Collection Exceptions   In many cases, if you reference a nonexistent collection element, then PL/SQL raises a predefined exception. Consider the illustration shown b

Update stock levels, At times, customers make mistakes in submitting their ...

At times, customers make mistakes in submitting their orders and call to cancel the order. Brewbean's wants to create a trigger that automatically updates the stock level of all pr

While-loop - iterative control, WHILE-LOOP The WHILE-LOOP statement rela...

WHILE-LOOP The WHILE-LOOP statement relates a condition with the series of statements enclosed by the keywords LOOP and END LOOP, as shown: WHILE condition LOOP sequence_of_sta

Cursor attributes in pl sql, Cursor Attributes   The Cursors and curso...

Cursor Attributes   The Cursors and cursor variables have 4 attributes which give you helpful information about the execution of a data manipulation statement. Syntax:

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