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

Remote operations in pl sql, Remote Operations: As the illustration sh...

Remote Operations: As the illustration shows below, the PL/SQL subprograms can execute the dynamic SQL statements which refer to the objects on a remote database: PROCEDURE

Stored subprograms, Stored Subprograms Normally, tools (like Oracle Fo...

Stored Subprograms Normally, tools (like Oracle Forms) which incorporate the PL/SQL engine can store subprograms locally for later, strictly local execution. Though, to become

%found - explicit cursor attributes, %FOUND Subsequent to a cursor or ...

%FOUND Subsequent to a cursor or cursor variable is opened but before the first fetch, the %FOUND yields NULL. Afterward, it yields TRUE when the last fetch returned a row, or

%notfound - implicit cursor attributes, %NOTFOUND The %NOTFOUND is the...

%NOTFOUND The %NOTFOUND is the logical opposite of the %FOUND. The %NOTFOUND yields TRUE when an INSERT, UPDATE, or DELETE statement affected no rows, or the SELECT INTO state

When or then key constraints, WHEN or THEN Key Constraints Suppose a t...

WHEN or THEN Key Constraints Suppose a table has two columns representing a period of time throughout which the information conveyed by the other columns is recorded as having

Introduction to oracle, Introduction Oracle 9i - it was made publ...

Introduction Oracle 9i - it was made public in the year 2001 with over 400 features, and graphics, it has merged the traditional business with modern internet application

Using set transaction, Using SET TRANSACTION You use the SET TRANSACTI...

Using SET TRANSACTION You use the SET TRANSACTION statement to begin the read-only or read-write transaction, start an isolation level, or assign your present transaction to a

Execute your documentation in oracle, Using research notes and Oracle docum...

Using research notes and Oracle documentation plan and execute an upgrade of an installation of Oracle 10g to Oracle 11g release 1. To do this you must show in screen shots and wri

Exception handling, set serveroutput on declare a number(5); b n...

set serveroutput on declare a number(5); b number(5); c number(5); begin a:=&a; b:=&b; c:=a/b; dbms_output.put_line(c); exception when zero_d

Sql queries, SELECT a.child_fname,a.child_lname,concat(b.parent_title,b.par...

SELECT a.child_fname,a.child_lname,concat(b.parent_title,b.parent_fname), b.parent_lname,b.parent_tphone FROM child a,parent b WHERE a.parent_id=b.parent_id ORDER BY a.child_fnam

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