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
Comparison Operators The Comparison operators can compare one expression to another. The outcome is always true, false, or null. Usually, you use a comparison operators in condi

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

Parameter and Keyword Description: dynamic_string: This is a string variable, literal, or expression which represents a SQL statement or the PL/SQL block. define_vari

Positional and Named Notation You can write the actual parameters when calling a subprogram, using either positional or named notation. That is, you can point to the relationsh

IN Mode An IN parameter pass the values to the subprogram being called. Within the subprogram, an IN parameter acts like a constant. And hence, it cannot be assigned a value.

MAX and MIN operator in SQL Example: (SELECT MAX (Mark) FROM EXAM_MARK WHERE StudentId = 'S1') (SELECT MIN (Mark) FROM EXAM_MARK WHERE StudentId = 'S1') Example

Assignment Source Not a Literal - Variable Syntax: SET SN = SID (SUBSTRING (SN.C FROM 1 FOR 1)||'5');

Example of Foreign Key Constraint Example: Alternative formulation for 6.3 as a foreign key constraint ALTER TABLE EXAM_MARK ADD CONSTRAINT Must_be_enrolled_to_take_exam

1. Create a procedure called TAX_COST_SP to accomplish the tax calculation task. Keep in mind that the state and subtotal values are inputs into the procedure and the procedure is

Write a pl/sql block that declares and uses cursors with parameters. In a loop, use a cursor to retrieve the department number and the department name from the departments table