Functions in pl/sql, PL-SQL Programming

Functions 

The function is a subprogram that calculates a value. The Functions and procedures are structured similar, except that the functions have a RETURN clause. You can write functions using the syntax as shown below:

FUNCTION name [(parameter[, parameter, ...])] RETURN datatype IS

[local declarations]

BEGIN

executable statements

[EXCEPTION

exception handlers]

END [name];

Where the parameter stand for the following syntax which is as shown below:

parameter_name [IN | OUT [NOCOPY] | IN OUT [NOCOPY]] datatype_name

[{:= | DEFAULT} expression]

The datatype of a parameter or function result cannot be constrained. Though, you can use a workaround to size-constrain them indirectly.

Similar to a procedure, a function has 2 parts: the specifications & the body. The function specification starts with the keyword FUNCTION and ends with the RETURN clause that specifies the datatype of the result value. The Parameter declarations are not obligatory.

The Functions that take no parameters are written without the parentheses. The function body starts with the keyword IS and ends with the keyword END followed by an optional function name. The function body has 3 parts: a declarative section, an executable section, & an optional exception-handling section.

The declarative section contains the local declarations, that are placed between the keywords IS & BEGIN. The keywords DECLARE is never used. The executable section contains statements that are placed between the keywords BEGIN and EXCEPTION (or END). One or more RETURN statements should appear in the executable section of a function. The exception-handling section contains exception handlers that are placed between the keywords EXCEPTION and END. Consider the function sal_ok, that determines if an employee salary is out of range:

FUNCTION sal_ok (salary REAL, title REAL) RETURN BOOLEAN IS

min_sal REAL;

max_sal REAL;

BEGIN

SELECT losal, hisal INTO min_sal, max_sal

FROM sals

WHERE job = title;

RETURN (salary >= min_sal) AND (salary <= max_sal);

END sal_ok;

Whenever called, this function accepts an employee salary and the job title. It uses the job title to select the range limits from the sals database table. The sal_ok, function identifier, is set to a Boolean value by the RETURN statement. When the salary is out of range, the sal_ok is set to FALSE; or else, the sal_ok is set to TRUE.

The function is called as the part of an expression. For illustration, the function sal_ok might be called as shown:

DECLARE

new_sal REAL;

new_title VARCHAR2(15);

BEGIN

...

IF sal_ok(new_sal, new_title) THEN ...

The function identifier sal_ok acts such as a variable whose value depends on the parameters passed to it.

Posted Date: 10/5/2012 5:24:10 AM | Location : United States







Related Discussions:- Functions in pl/sql, Assignment Help, Ask Question on Functions in pl/sql, Get Answer, Expert's Help, Functions in pl/sql Discussions

Write discussion on Functions in pl/sql
Your posts are moderated
Related Questions
Indeterminacy in SQL Some SQL expressions are actually not function invocations at all in the mathematical sense, being indeterminate-invocations operating on identical input

Special cases of projection This section describes the identity projection, r {ALL BUT}, and the projection on no attributes, r { }, which yields TABLE_DUM when r is empty, ot

Running the PL/SQL Wrapper To run the PL/SQL Wrapper, go through the wrap command at your operating system prompt by using the syntax as shown: wrap iname=input_file [oname=

EXECUTE IMMEDIATE Statement   The EXECUTE IMMEDIATE statement prepare (parses) and instantly executes a dynamic SQL statement or an anonymous PL/SQL block. Syntax:

Enrolment was split - SQL Example shows how relvars IS_CALLED and IS_ENROLLED_ON can be derived from the original ENROLMENT relvar, using projection in the initial assignment

Methods: In normal, a method is a subprogram declared in an object type specification using the keyword MEMBER or STATIC. The method cannot have similar name as the object typ

Projection in SQL - correct version Student StudentId is enrolled on some course. SELECT DISTINCT StudentId FROM IS_ENROLLED_ON In more complicated examples it is someti

Data Types in SQL - Timestamp TIMESTAMP for values representing points in time on a specified uniform scale. DATE is used for timestamps on a scale of one day, such as DATE '2

Bulk Fetching The illustration below shows that you can bulk-fetch from a cursor into one or more collections: DECLARE TYPE NameTab IS TABLE OF emp.ename%TYPE; TYPE S

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