Chapter09

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

Lesson A Objectives After completing this lesson, you should be able to: Create and use indexes Work with PL/SQL stored program units Create server-side stored program units in SQL*Plus Use Forms Builder to create stored program units

Database Indexes Database table index Distinct database table Contains data values with corresponding columns that specify physical locations of records that contain data values ROWID Internal location of record in database Encoded using internal data format

Database Indexes (continued) Index on specific table field ROWID value Sorted indexed field value Oracle 10 g automatically creates index on table’s primary key Create indexes on columns that users often use in search conditions

Creating an Index Create after adding data Syntax: CREATE INDEX index_name ON tablename ( index_fieldname );

Creating Composite Indexes Composite index Multiple sorted columns For queries that contain multiple search conditions primary search field Secondary search field Syntax: CREATE INDEX index_name ON tablename ( index_fieldname1 , index_fieldname2 , …);

Viewing Index Information Using the Data Dictionary Views Query data dictionary views Retrieve information about database objects Retrieve index information

Querying the USER_INDEXES Data Dictionary View (Partial Output Shown)

Dropping an Index Drop index when: Applications no longer use queries aided by index Index does not improve query performance Enough to justify overhead created on insert, update, and delete operations Syntax: DROP INDEX index_name ;

Determining When to Create an Index Create index when: Table contains large number of records Field contains wide range of values Field contains large number of null values Queries frequently use field in search condition or join condition Most queries retrieve less than 2% to 4% of table rows

Determining When to Create an Index (continued) Do not create index when: Table does not contain large number of records Applications do not use proposed index field in query search condition Most queries retrieve more than 2% to 4% of table records Applications frequently insert or modify table data Decision based on judgment and experience

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

Types of Oracle 10 g Stored Program Units

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

Stored Program Unit Procedures CREATE_PROCEDURE command Header Parameter declarations list Program unit body Exception section

Syntax to Create a Stored Program Unit Procedure

Creating the Parameter Declarations List Defines parameters Declares associated data types Parameter mode IN OUT IN OUT

Creating a Stored Procedure in SQL*Plus

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

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 , ...);

Passing Parameters to a Procedure

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);

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

Commands to Create a Stored Program Unit Function

Calling a Function Syntax: variable_name := function_name ( parameter1 , parameter2 , ...); Variables passed for parameter values Must be in same order as parameters appear in function declaration

Using Forms Builder to Create Stored Procedures and Functions Create and test program unit within form Save as stored program unit in database schema Advantage of using Forms Builder Provides enhanced development and debugging environment PL/SQL Editor

Creating, Testing, and Saving a Stored Program Unit Procedure in Forms Builder Create stored procedure in test form Create form trigger to test program unit procedure Save program unit as stored procedure in database Database Objects node Contains child nodes that represent every database user

Creating, Testing, and Saving a Stored Program Unit Function in Forms Builder (continued) Create program unit function in Forms Builder Test program unit function Save program unit form as stored program unit in database

Lesson A Summary Database table index ROWID Stored program units Procedure Function Use Forms Builder PL/SQL Editor to develop stored program units

Lesson B Objectives After completing this lesson, you should be able to: Call stored procedures from other stored procedures and pass parameter values Create libraries Create packages Create database triggers

Calling Stored Program Units From Other Stored Program Units Decompose applications into logical units of work Write individual program units for each logical unit Code is in single location Call stored program unit from another stored program unit Execute PL/SQL command that specifies Name of called program unit Parameter value list

Calling Stored Program Units From Other Stored Program Units (continued) Must create called program unit before calling program unit Otherwise compile error

PL/SQL Libraries Operating system file Contains code for multiple related procedures and functions Attach to: Form Report Another library Stored in client workstation

PL/SQL Libraries (continued) Extensions: .pll .plx Advantage of using library over multiple stored program units: Library places commands for multiple related program units in single location Always executes on client workstation

Creating a PL/SQL Library Use Forms Builder to: Create libraries Add form program units and stored program units to library Save library .pll file in file system of workstation or shared network drive Click Compile Module button Generate .plx file

Attaching a Library to a Form Select form’s Attached Libraries node Click Create button Specify PL/SQL library .pll filename Message appears to store folder path information for library Include path information for library Library .pll file must always be available at specified folder path and filename Otherwise store in default form folder

Modifying Library Program Units When program unit within library requires maintenance: Open library in Forms Builder Modify program unit as necessary Compile program unit within library Recompile library to create new .plx file Forms that contain library as attached library object then use modified code

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

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

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

General Syntax for a Package Specification

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 , ...);

The Package Specification (continued) Declare function syntax: FUNCTION function_name ( parameter1 parameter1_data_type , parameter2 parameter2_data_type , ...) RETURN return_datatype ;

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

General Syntax for a Package Body

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

The Package Body (continued) Package exists in user schema Must grant permission to others GRANT EXECUTE ON package_name TO username ;

Creating a Package in Forms Builder Create package specification in Forms Builder Create package body in Forms Builder Save package in database

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

Database Trigger Properties Trigger timing BEFORE AFTER Trigger statement INSERT UPDATE DELETE

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

Creating Database Triggers Database trigger header Trigger body

General Syntax to Create a Trigger in SQL*Plus

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

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];

Viewing Information About Triggers USER_TRIGGERS data dictionary view Contains information about triggers

Lesson B Summary PL/SQL library Package Database trigger Activated when table modified

Chapter09

More Related Content

What's hot (20)

Similar to Chapter09 (20)

Recently uploaded (20)

Chapter09