Pl/sql conditional control: if statements, PL-SQL Programming

Assignment Help:

Pl/sql Conditional Control: IF statements

Frequently, it is necessary to take the alternative actions depending on the circumstances. The IF statement execute a series of statements conditionally. That is, whether the series is executed or not depends on the value of the condition. There are 3 forms of IF statements: IF-THEN, IF-THEN-ELSE, & IF-THEN-ELSIF.


IF-THEN

The simplest form of the IF statement acquaintances a condition with a series of statements enclosed by the keywords THEN and END IF (not ENDIF), as shown below:


IF condition THEN
sequence_of_statements
END IF;

The series of statements is executed only if the condition is true. When the condition is false or null, then the IF statement can do nothing. In either of the case, the control passes to the next statement. An illustration is shown below:


IF sales > quota THEN
compute_bonus(empid);
UPDATE payroll SET pay = pay + bonus WHERE empno = emp_id;
END IF;

You may want to place brief IF statements on a single line, as in

IF x > y THEN high := x; END IF;



IF-THEN-ELSE

The IF statement that is the second form adds the keyword ELSE follow by an alternative series of statements is as shown below:


IF condition THEN
sequence_of_statements1
ELSE
sequence_of_statements2
END IF;


The series of statements in the ELSE clause is executed only if the condition is false or null. Therefore, the ELSE clause ensure that a sequence of statements is executed. In the example below, the first UPDATE statement is executed if the condition is true, while  the second UPDATE statement is executed if the condition is false or null:


IF trans_type = ’CR’ THEN
UPDATE accounts SET balance = balance + credit WHERE...
ELSE
UPDATE accounts SET balance = balance - debit WHERE...
END IF;


The THEN and ELSE clauses can involve the IF statements. That is, the IF statements can be nested, as the example below shows:

IF trans_type = ’CR’ THEN
UPDATE accounts SET balance = balance + credit WHERE...
ELSE
IF new_balance >= minimum_balance THEN
UPDATE accounts SET balance = balance - debit WHERE ...
ELSE
RAISE insufficient_funds;
END IF;
END IF;


IF-THEN-ELSIF

At many times you want to select an action from some mutually exclusive alternatives. The third form of the IF statement uses the keyword ELSIF to introduce the additional conditions which is as shown below:

IF condition1 THEN
sequence_of_statements1
ELSIF condition2 THEN
sequence_of_statements2
ELSE
sequence_of_statements3
END IF;


When the first condition is false or null, then the ELSIF clause tests another condition. An IF statement can have a few number of ELSIF clauses; the final ELSE clause is elective. The Conditions are evaluated one by one from top to bottom. When any condition is true, its related sequence of statements is executed and the control passes to the next statement. If all the conditions are false or null, then the sequence in the ELSE clause is executed. Consider the following illustration as shown below:


BEGIN
...
IF sales > 50000 THEN
bonus := 1500;
ELSIF sales > 35000 THEN
bonus := 500;
ELSE
bonus := 100;
END IF;
INSERT INTO payroll VALUES (emp_id, bonus, ...);
END;


When the value of sales is bigger than 50000, the first and second conditions are true.
However, bonus is assigned the proper value of 1500 as the second condition is never tested. When the first condition is true, its related statement is executed and the control passes to the INSERT statement.


Related Discussions:- Pl/sql conditional control: if statements

Rollback behavior - bulk bind performance improvement, Rollback Behavior ...

Rollback Behavior When a FORALL statement fails, the database changes are rolled back to an implicit savepoint marked before each of the SQL statement execution. The Changes t

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

Other monadic - sql, Other monadic - SQL In 2VL there are just 4 (2 2 ...

Other monadic - SQL In 2VL there are just 4 (2 2 ) monadic operators, of which negation is really the only "useful" one. When a third truth value is introduced we have 27 (3 3

Projection and existential quantification - sql, Projection and Existential...

Projection and Existential Quantification - SQL Intuitively it might seem that projection in SQL is simply a matter of specifying the required columns in the SELECT clause, a

Join query, Using a join on 3 tables, select 5 columns and 10 rows from the...

Using a join on 3 tables, select 5 columns and 10 rows from the 3 tables without the use of a Cartesian product Query: SELECT E.LAST_NAME, E.FIRST_NAME, S.BUILDING, S.BRAN

Primary key - sql, Primary Key - SQL A PRIMARY KEY specification carri...

Primary Key - SQL A PRIMARY KEY specification carries an implicit NOT NULL constraint on each column of the specified key. When more than one key constraint is required, the k

Advantages of invoker rights, Advantages of Invoker Rights The Invoker-...

Advantages of Invoker Rights The Invoker-rights routines centralize the data retrieval. They are particularly helpful in applications which store data in various schemas. In su

%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

Using operator value in pl sql, Using Operator VALUE: As you may expec...

Using Operator VALUE: As you may expect, the operator VALUE returns the value of an object. The VALUE takes its argument a correlation variable.  For illustration, to return a

Conditionals - sql, Conditionals - SQL At first sight SQL does not app...

Conditionals - SQL At first sight SQL does not appear to have a single operator for expressing logical implication. In this respect it would be in common with most programming

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