Chapter 9:
Advanced SQL and PL/SQL
Guide to Oracle 10g
Lesson A Objectives
After completing this lesson, you should be able to:
• Work with PL/SQL stored units
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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
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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.
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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
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Creating Procedures
• CREATE [OR REPLACE] PROCEDURE procedure_name
[ (parameter mod datatype [,parameter]) ]
Header
IS
Section
[local variable declaration_section]
BEGIN
body
executable_section
[EXCEPTION
Exception
exception_section]
section
END [procedure_name];
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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
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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.
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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.
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Creating Procedures (Example)
• The (%ROWTYPE) reference data type creates
Data Size
composite variables that reference theNO
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.
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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.
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Calling a Stored Procedure
1. 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
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Calling a Stored Procedure
• Calling stored procedure from separate PL/SQL
program
– Similar to calling stored procedure from SQL*Plus
command line
– Omit EXECUTE command
update_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.
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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.
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Creating Functions
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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
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Calling a Functions
• Pay attention to to_date function.
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End of Chapter 9:
Advanced SQL and PL/SQL
Guide to Oracle 10g