Chapter 9: Advanced SQL and PL/SQL Guide to Oracle 10g.

Chapter 9: Advanced SQL and PL/SQL

Guide to Oracle 10g

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Guide to Oracle 10g 2

Lesson A Objectives

After completing this lesson, you should be able to:• Work with PL/SQL stored units


PL/SQL Stored Program Units• A program unit is a self-contained group of program

statements that can be used within a large program• PL/SQL part written in the form builder that may be

called by a form trigger is an example of a unit.• The unit you created and executed so far in a form

builder or SQL*Plus are anonymous PL/SQL programs which are– Programs submitted to the interpreter and run– Do not interact with other program units– They only exist within forms


PL/SQL Stored Program Units

• Stored PL/SQL program units are:– program units that other PL/SQL program can

reference, – and that other database users can use and execute.

• What do stored units can do?– It can receive input values from other program units– It can pass output values to other program units

• Stored unit can be linked to database application components created in Form builder to enhance their functionality.


PL/SQL Stored Program Units

• It can be either– Server-side program units: stored as database

object and execute on the sever (can be used by all users)

– Client-side program units: stored in the file system of a client workstation and execute on the client workstation

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Creating Stored program Units

• Stored program units can be either:– Procedures:

• Can receive multiple input parameters and return multiple output values (or no output values)

• Can perform an action such insert, update or delete record

– Functions:• Can receive multiple input parameters and always returns

a single output value


Creating Procedures

• CREATE [OR REPLACE] PROCEDURE procedure_name [ (parameter mod datatype [,parameter]) ]

IS

[local variable declaration_section]

BEGIN

executable_section

[EXCEPTION

exception_section]

END [procedure_name];

HeaderSection

body

Exception section


Creating Procedures

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Creating Procedures• The header section defines:

– The procedure name (name should be unique )

– The parameters that the procedure receives or delivers (IN, OUT, IN OUT)

– IS keyword: follows the parameters list

– The local procedure variables

• Create or replace: instructs the DBMS to create the procedure if it does it exists, otherwise; it replaces the existing one

• OR REPLACE clause is optional. But if omitted and a procedure exists with the same name, an error occurs

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Creating Procedures (parameters list)

• Parameter name, mod and data type are enclosed in parentheses, each is separated by a comma.

• Parameter mod: describes how the procedure change the value. It can be:– IN: passed parameter is a Read only value. Cannot be

changed by the procedure

– OUT: write-only value. Always comes on the left side of an assignment statement

– IN OUT: its value can be changed


Creating Procedures (parameters list)

• The data type cannot specify a length, precision, or scale value for a numerical data type, or maximum length of a character data type.

• Oracle Database derives the length, precision, or scale of the return value from the environment from which the function is called.

• When the procedure or function is created and debugged, it ca be called from any application.


Creating Procedures (Example)

• UPDATE_ENROLLMENT_GRADE: a procedure that updates a student’s grade for a course.

• It accepts 3 input parameters (student ID, Course section ID and grade)

• Upon successful, the stored procedure exists as an object in your schema.


Creating Procedures (Example)

• The (%ROWTYPE) reference data type creates composite variables that reference the entire data record.– Faculty_row FACULTY%ROWTYPE;

• The variable faculty_row references all of the columns in the FACULTY table, and each column has the same data type as its associated DB column.

NO Data Size


Debugging program units (SQL*Plus)

• Interpreter displays only a warning message. It does not contain a compiler error message nor a line location.

• Instead, it writes all compiler errors to a system table accessed using USER_ERRORS data dictionary view.

• It displays a summary listing of compile errors generated by the last program unit that was compiled.

• Use the SHOW ERRORS command:• See Figure 9-12.


Calling a Stored Procedure1. Execute directly from SQL*Plus command line

2. Create separate PL/SQL program that contains – Command to call stored procedure

– Passes parameter values to procedure

• Calling stored procedure from SQL*Plus command line:EXECUTE procedure_name

(parameter1_value, parameter2_value, ...);

Execute update_enrollment_grade(‘MA100’, 12, ‘B’);

– Single quote for character is important.

– Variables passed for each parameter must be in same order as parameters appear in parameter declarations list


Calling a Stored Procedure• Calling stored procedure from separate PL/SQL

program– Similar to calling stored procedure from SQL*Plus

command line

– Omit EXECUTE commandupdate_enrollment_grade(‘MA100’, 12, ‘B’);

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Creating Functions

• A function is similar to a procedure, except that it returns a single value.


Creating Functions• The function name (name should be unique )• The syntax of the parameter list is identical to that of

the procedure.• After the parameters list, RETURN sentence determines

the data type of the return value of the function. (remember that procedure does not return a value, so it contains NO Return statement)

• After IS, the return_value_variable declares the variable that represents the function return value.


Creating Functions


Calling a Functions

• Calling a function requires assignment the command to a previously declared variable in the calling program, since the function returns a single data value.variable_name := function_name(parameter1, parameter2, ...);

• Variables passed for parameter values– Must be in same order as parameters appear in

function declaration


Calling a Functions

• Pay attention to to_date function.

End of Chapter 9: Advanced SQL and PL/SQL

Guide to Oracle 10g

Author

Global to this PPT: Please note that most figure slides have figure caption as slide title, not heading - okay? (The individual slides are commented.)

Chapter 9: Advanced SQL and PL/SQL Guide to Oracle 10g.

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