1. Advanced SQL and PL/SQL Topics

2. Overview of PL/SQL Stored Program
Units
• Program unit
– Self-contained group of program statements that
can be used within larger program
•
•
•
•
Anonymous PL/SQL programs
Stored PL/SQL program units
Server-side program units
Client-side program units
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3. Types of Oracle 10g Stored Program
Units
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4. Creating Stored Program Units
• Procedure
– Receive multiple input parameters
– Return multiple output values or return no output
values
– Perform action such as inserting, updating, or
deleting database records
• Function
– Receive multiple input parameters
– Always returns single output value
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5. Stored Program Unit Procedures
• CREATE_PROCEDURE command
–
–
–
–
Header
Parameter declarations list
Program unit body
Exception section
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6. Syntax to Create a Stored Program
Unit Procedure
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7. Creating the Parameter Declarations
List
• Defines parameters
• Declares associated data types
• Parameter mode
– IN
– OUT
– IN OUT
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8. Creating a Stored Procedure in
SQL*Plus
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9. Debugging Stored Program Units in
SQL*Plus
• Similar to debugging any program
• Identify program line causing error
• SQL*Plus interpreter displays error warning
message
– Does not automatically display compile error
messages and line locations
– Writes all compile errors to system table
• Access using USER_ERRORS data dictionary view
• Execute SHOW ERRORS command
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10. Calling a Stored Procedure
• Execute directly from SQL*Plus command line
• 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, ...);
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11. Passing Parameters to a Procedure
•IN The value of the parameter is passed into the procedure when the
procedure is invoked. It is similar to read-only
•OUT Any value the parameter has when it is called is ignored. When the
procedure finishes, any value assigned to the parameter during its execution is
returned to the calling environment. It is similar to write-only IN OUT This
mode is a combination of both IN and OUT. The value of the parameter can be
passed into the procedure when the procedure is invoked. It is then
manipulated within the procedure and returned to the calling environment. It is
similar to read-write
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12. Calling a Stored Procedure
(continued)
• Variables passed for each parameter
– Must be in same order as parameters appear in
parameter declarations list
• 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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13. Creating a Stored Program Unit
Function
• Use CREATE OR REPLACE FUNCTION
command
• function_return_value_datatype
– Defines data type that function returns
• return_value_variable
– Declares variable that represents function return
value
• RETURN command
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14. Commands to Create a Stored
Program Unit Function
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15. Calling a Function
• Syntax:
variable_name :=
function_name(parameter1, paramete
r2, ...);
• Variables passed for parameter values
– Must be in same order as parameters appear in
function declaration
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16. Packages
• Code library containing related program units and
variables
• Stored in database
• Executes on database server
• Grant other users privilege to use package
– Any PL/SQL program can reference package
procedures and functions
• More functionality than PL/SQL libraries
• More convenient to use than PL/SQL libraries
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17. The Package Specification
• Also called package header
• Declares public package objects, including:
–
–
–
–
Variables
Cursors
Procedures
Functions
• Made public
– Program units outside package can reference
package’s objects
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18. The Package Specification (continued)
• Public variables
– Visible to many different PL/SQL programs
– Values remain in memory even after programs that
declare and reference them terminate
– Declare public variable in DECLARE section of
package
• Same syntax used to declare private variable
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19. General Syntax for a Package
Specification
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20. The Package Specification (continued)
• Declare variables and cursors in packages
– Same syntax used in other PL/SQL programs
• Declare procedure syntax:
PROCEDURE procedure_name
(parameter1 parameter1_data_type,
parameter2 parameter2_data_type, ...);
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21. The Package Specification (continued)
• Declare function syntax:
FUNCTION function_name
(parameter1 parameter1_data_type,
parameter2 parameter2_data_type, ...)
RETURN return_datatype;
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22. The Package Body
• Contains commands to create program units that
package specification declares
• Must create specification before body
• Optional
• Variables declared at beginning of package body
– Private to package
• Each program unit in package specification must
be defined
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23. General Syntax for a Package Body
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24. The Package Body (continued)
•
•
•
•
Create package using SQL*Plus
Create package specification in SQL*Plus
Create package body in SQL*Plus
Reference package objects syntax:
– package_name.item_name
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25. The Package Body (continued)
• Package exists in user schema
– Must grant permission to others
– GRANT EXECUTE ON package_name TO
username;
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26. Database Triggers
• Program units
– Execute in response to database events of
inserting, updating, or deleting record
• Different from form triggers
• Useful for maintaining integrity constraints
• Similar to other program units
– But cannot accept parameters
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27. Database Trigger Properties
• Trigger timing
– BEFORE
– AFTER
• Trigger statement
– INSERT
– UPDATE
– DELETE
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28. Database Trigger Properties
(continued)
• Trigger level
– Statement-level
– Row-level
• Reference value of field in current record
– Both before and after triggering statement executes
• :OLD.fieldname
• :NEW.fieldname
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29. Creating Database Triggers
• Database trigger header
• Trigger body
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30. General Syntax to Create a Trigger in
SQL*Plus
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31. Creating Database Triggers to Leave
an Audit Trail for the Northwoods
University ENROLLMENT Table
• Track when users insert, update, and delete table
records
• Create trigger that leaves audit trail
– Create one or more tables to store audit trail values
• Create database trigger in SQL*Plus
• Create database trigger in Forms Builder
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32. Disabling and Dropping Triggers
• Drop trigger when not needed:
– DROP TRIGGER trigger_name;
• Disable trigger
– Trigger still exists in user’s database schema
– No longer fires when triggering event occurs
– Syntax:
• ALTER TRIGGER trigger_name [ENABLE
| DISABLE];
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33. Viewing Information About Triggers
• USER_TRIGGERS data dictionary view
– Contains information about triggers
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