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A Guide to Oracle9i1 Advanced SQL And PL/SQL Topics Chapter 9.

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Presentation on theme: "A Guide to Oracle9i1 Advanced SQL And PL/SQL Topics Chapter 9."— Presentation transcript:

1 A Guide to Oracle9i1 Advanced SQL And PL/SQL Topics Chapter 9

2 A Guide to Oracle9i2 Lesson A Objectives Learn how to create and use indexes Become familiar with PL/SQL stored program units Learn how to create server-side stored program units in SQL*Plus Learn how to use Forms Builder to create stored program units

3 A Guide to Oracle9i3 Database Indexes Similar to an index in a book Table with list of sorted data values and corresponding physical location Used to speed searches Uses ROWID column to represent physical location Primary key indexed automatically Unlimited number allowed, but more indexes means more processing time for action queries (insert, update, delete)

4 A Guide to Oracle9i4 Creating an Index Create index after table data is loaded CREATE INDEX index_name ON tablename (index_fieldname); Convention for naming index: tablename_fieldname.

5 A Guide to Oracle9i5 Composite Index Contains multiple (up to 16) sorted columns Used for queries with multiple search conditions CREATE INDEX index_name ON tablename(index_fieldname1, index_fieldname2, …);

6 A Guide to Oracle9i6 Viewing Index Information Use data dictionary view USER_INDEXES

7 A Guide to Oracle9i7 Dropping an Index If an index is no longer needed or does not improve performance, delete it DROP INDEX index_name;

8 A Guide to Oracle9i8 Use an Index When Table contains a large number of records (a rule of thumb is that a large table contains over 100,000 records) The field contains a wide range of values The field contains a large number of NULL values Application queries frequently use the field in a search condition or join condition Most queries retrieve less than 2% to 4% of the table rows

9 A Guide to Oracle9i9 Do Not Use an Index When The table does not contain a large number of records Applications do not use the proposed index field in a query search condition Most queries retrieve more than 2% to 4% of the table records Applications frequently insert or modify table data

10 A Guide to Oracle9i10 Overview of PL/SQL Stored Program Units Self-contained group of program statements that can be used within a larger program. Easier to conceptualize, design, and debug Save valuable programming time because you can reuse them in multiple database applications Other PL/SQL programs can reference them

11 A Guide to Oracle9i11 Overview of PL/SQL Stored Program Units Server-side program units — stored in the database as database objects and execute on the database server Client-side program units — stored in the file system of the client workstation and execute on the client workstation

12 A Guide to Oracle9i12 Types of Program Units

13 A Guide to Oracle9i13 Creating Stored Program Units Procedure: a program unit that can receive multiple input parameters and return multiple output values or return no output values Function: a program unit that can receive multiple input parameters, and always returns a single output value.

14 A Guide to Oracle9i14 Parameter Declarations List Defines the parameters and declares their associated data types Enclosed in parentheses Separated by commas

15 A Guide to Oracle9i15 Parameter Declarations List Parameter mode describes how the program unit can change the parameter value: –IN - specifies a parameter that is passed to the program unit as a read-only value that the program unit cannot change. –OUT - specifies a parameter that is a write-only value that can appear only on the left side of an assignment statement in the program unit –IN OUT - specifies a parameter that is passed to the program unit, and whose value can also be changed within the program unit

16 A Guide to Oracle9i16 Creating a Stored Procedure in SQL*Plus

17 A Guide to Oracle9i17 Debugging Stored Program Units in SQL*Plus

18 A Guide to Oracle9i18 Debugging Stored Program Units in SQL*Plus

19 A Guide to Oracle9i19 Calling a Stored Procedure From SQL*Plus command line: –EXECUTE procedure_name (parameter1_value, parameter2_value,...); From PL/SQL program: –Omit execute command Passing parameters (see Figure 9-13)

20 A Guide to Oracle9i20 Creating a Stored Program Unit Function

21 A Guide to Oracle9i21 Creating a Stored Program Unit Function Last command in function must be RETURN

22 A Guide to Oracle9i22 Calling a Function variable_name := function_name(parameter1, parameter2,...);

23 A Guide to Oracle9i23 Using Forms Builder to Create Stored Procedures and Functions Create and test the program unit within a form Save it as a stored program unit in your database schema Provides an enhanced development and debugging environment: –Color-coded editor for entering and debugging program unit commands –Displays compile error messages immediately –Use the Forms Debugger to step through program unit commands and view how variable values change

24 A Guide to Oracle9i24 Using Forms Builder to Create Stored Procedures and Functions Create the procedure or function as a form program unit Test and debug the form program unit by calling it from commands within a form trigger Save the form program unit as a stored program unit in the database

25 A Guide to Oracle9i25 Lesson B Objectives Learn how to call stored procedures from other stored procedures and pass parameter values Create libraries Create packages Create database triggers

26 A Guide to Oracle9i26 Calling Stored Program Units from Other Stored Program Units Decompose applications into logical units of work and then write individual program units for each logical unit Code is in a single location Developers do not need to rewrite program units that already exist References procedures must be declared first

27 A Guide to Oracle9i27 PL/SQL Libraries Operating system file that contains code for multiple related procedures and functions Attach a PL/SQL library to a form or report –Triggers within the form or report reference library’s procedures and functions Store a PL/SQL library in the file system of the client workstation.pll extension - stands for “PL/SQL Library” Compile the library into a library executable file -.plx extension - stands for “PL/SQL Library Executable” Library places the commands for multiple related program units in a single location that developers can access and use

28 A Guide to Oracle9i28 Creating a PL/SQL Library Use Forms Builder to create libraries Add form program units and stored program units to the library.

29 A Guide to Oracle9i29 Packages Another way to make PL/SQL program units available to multiple applications A code library that contains related program units and variables Stored in the database and executes on the database server Have more functionality than PL/SQL libraries: –Can create variables in packages –Definitions for explicit cursors –More convenient to use than PL/SQL libraries –Available without explicitly attaching them to a form or report

30 A Guide to Oracle9i30 Package Specification Also called package header Declares package objects, including variables, cursors, procedures, and functions, Use to declare public variables: –Remain in memory after the programs that declare and reference them terminate –Declared in the DECLARE section of a package –Referenced same as private variables

31 A Guide to Oracle9i31 Package Specification

32 A Guide to Oracle9i32 Package Header Package_name identifies the package –Must adhere to the Oracle Naming Standard Declare the package objects in any order Package can consist of just variable declarations, or it can consist of just procedure or function declarations

33 A Guide to Oracle9i33 Procedure and Function Declarations Declare a procedure: PROCEDURE procedure_name (parameter1 parameter1_data_type, parameter2 parameter2_data_type,...); Declare a function: FUNCTION function_name (parameter1 parameter1_data_type, parameter2 parameter2_data_type,...) RETURN return_datatype;

34 A Guide to Oracle9i34 Package Body Contains the implementation of declared procedures and functions Specification comes before body Optional: sometimes a package contains only variable or cursor declarations, and no procedure or function declarations See Figure 9-35 for general syntax

35 A Guide to Oracle9i35 Package Body Package_name in the package body must be the same as package_name in the package specification Variables that you declare at the beginning of the package body are private to the package Each package program unit has its own declaration section and BEGIN and END statements Each program unit declared in the package body must have a matching program unit forward declaration in the package specification, with an identical parameter list

36 A Guide to Oracle9i36 Creating a Package Header in SQL*Plus

37 A Guide to Oracle9i37 Creating a Package Body in SQL*Plus

38 A Guide to Oracle9i38 Using Package Objects Must preface the item with the package name: –package_name.item_name. To grant other users the privilege to execute a package: –GRANT EXECUTE ON package_name TO username;

39 A Guide to Oracle9i39 Creating a Package in Forms Builder Create a program unit of type Package Spec Type the package specification in the PL/SQL editor Create a program unit of type Package Body Type package body in the PL/SQL editor Compile package body and test using a form trigger Save the package in the database for future use

40 A Guide to Oracle9i40 Database Triggers Program units that execute in response to the database events of inserting, updating, or deleting a record Different from form triggers Useful for maintaining integrity constraints and audit information Cannot accept input parameters Executes only when its triggering event occurs

41 A Guide to Oracle9i41 Trigger Properties Trigger timing: –Defines whether a trigger fires before or after the SQL statement executes –Can have the values BEFORE or AFTER Trigger statement: –Defines the type of SQL statement that causes a trigger to fire –Can be INSERT, UPDATE, or DELETE

42 A Guide to Oracle9i42 Trigger Properties Trigger level: –Defines whether a trigger fires once for each triggering statement or once for each row affected by the triggering statement –Can have the values ROW or STATEMENT –Statement-level triggers fire once, either before or after the SQL triggering statement executes. –Row-level triggers fire once for each row affected by the triggering statement Use :OLD.fieldname to reference previous value Use :NEW.fieldname to reference changed value

43 A Guide to Oracle9i43 Creating Database Triggers

44 A Guide to Oracle9i44 Database Trigger Header Trigger_name must follow Oracle Naming Standard Join statement types using the OR operator to fire for multiple statement types (INSERT OR UPDATE) WHEN (condition) clause: – Trigger will fire only for rows that satisfy a specific search condition –WHEN OLD.grade IS NOT NULL;

45 A Guide to Oracle9i45 Database Trigger Body Contains the commands that execute when the trigger fires PL/SQL code block that contains the usual declaration, body, and exception sections Cannot contain transaction control statements Reference the NEW and OLD field values only in a row-level trigger

46 A Guide to Oracle9i46 Trigger Use – Audit Trail

47 A Guide to Oracle9i47 Creating Audit Trigger in SQL*Plus

48 A Guide to Oracle9i48 Creating a Database Trigger in Forms Builder Use the Database Trigger Dialog Box to specify trigger properties Type trigger body into Trigger Body entry field

49 A Guide to Oracle9i49 Disabling and Dropping Triggers To remove a trigger: –DROP TRIGGER trigger_name; To disable/enable a trigger: –ALTER TRIGGER trigger_name [ENABLE | DISABLE];

50 A Guide to Oracle9i50 Viewing Trigger Information

51 A Guide to Oracle9i51 Summary Database indexes store an ordered list of field values with corresponding ROWID Indexes are used to speed query performance Stored program units are named PL/SQL blocks that are saved Procedures accept parameters and return 0,1, or many values Functions accept parameters and return exactly one value

52 A Guide to Oracle9i52 Summary PL/SQL Library is a client-side file containing procedures and functions PL/SQL Package is a collection of public variables, cursors, procedures and functions stored in the DBMS Database triggers are PL/SQL blocks that are run in response to table changes Database triggers are used to enforce integrity constraints and track changes Forms Builder may be used as an IDE to develop functions, procedures, libraries, packages and triggers

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