Oracle Database 11g Express Edition – PL/SQL and Database Administration Concepts
Slide 1:
Hello and welcome to this online, self-paced course titled Oracle Database 11g Express Edition – PL/SQL
and Database Administration Concepts. My name is Anupama Mandya, and I am part of Oracle
Corporation’s Curriculum Development team. This course is part of Oracle Database 11g Express Edition
New Features Self-Study series.
In this course, using demonstrations, I will be discussing some basic PL/SQL and Database Administration
Concepts using Oracle SQL Command Line and Oracle SQL Developer tools. This course is presented in
two parts.
Slide 2: Using the Player
Using The Player Script
Before we begin, take a look at some of the features of this Flash-based course player. If you’ve
attended similar Oracle eStudy courses in the past then, feel free to skip this slide.
To your left, you will find a hierarchical course outline. This course enables and even encourages you to
go at your own pace, which means you are free to skip over topics you already feel confident on, or
jump right to a feature that really interests you, or go back and review topics that were already covered.
Simply click on a course section to expand its contents and then select an individual slide. However, note
that by default we will automatically walk you through the entire course without requiring you to use
the outline.
To the right of the course outline tab is the transcripts tab, which contains any additional reference
notes for the current slide. Feel free to read these reference notes at the conclusion of the course. Or if
you prefer you can read them as we go along.
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Slide 3: About This Course
So, you know the title of the course, but you may be asking yourself “Am I in the right place?” To help
you answer these questions you can answer information here regarding the course objectives, target
audience and the prerequisites. When finished, click the “Next Topic” button.
Slide 4: Road Map
The first topic in this course is Getting familiar with the commonly used terms in PL/SQL
Slide5: FAQ
Introduction:
In this topic, we discuss what PL/SQL is and the commonly used terms in PL/SQL. Click on each of the
tabs to uncover the answers to some of the commonly asked questions.
What is PL/SQL?
Procedural Language/SQL (PL/SQL) (pronounced as P L sequel) is a native Oracle Database Express
Edition extension to SQL. It bridges the gap between declarative and imperative program control by
adding procedural elements, such as conditional control and loops.
In PL/SQL, you can declare constants and variables, procedures and functions, types and variables of
those types, and triggers. You can handle exceptions (run-time errors). You can create PL/SQL units likeprocedures, functions, packages, types, and triggers-that are stored in the database for reuse by
applications that use any of the Oracle Database XE programmatic interfaces.
The language offers a robust programming environment that enables you to program procedurally
and/or with object-oriented programming techniques such as encapsulation, information hiding, and
function overloading.
With PL/SQL, you can use the state-of-the-art programming for the Oracle Database server and toolset.
Why use PL/SQL?
The following are the major benefits of using PL/SQL :
Integration of procedural constructs with SQL
PL/SQL integrates control statements and conditional statements with SQL. This gives you a better
control of SQL statements and their execution.
Reduction in network congestion
PL/SQL allows you to logically combine SQL statements as one unit. The application can send the entire
block to the database instead of sending the SQL statements one at a time. This reduces the network
traffic.
Modularized program development
PL/SQL allows you to group logically related statements within blocks. You can nest blocks inside larger
blocks to build powerful program. Also, you can break your application into smaller modules.
Integration with tools
The PL/SQL engine is integrated in Oracle tools such as HTML Database, Oracle Database XE, Oracle
Forms, Oracle Reports and so on. When you use these tools, the locally available PL/SQL engine
processes the procedural statements and only the SQL statements are passed to the database.
What is a Sub Program?
A subprogram is a PL/SQL unit that consists of SQL and PL/SQL statements that solve a specific problem
or perform a set of related tasks.
A subprogram can have parameters, whose values are supplied by the invoker. A subprogram can be
either a procedure or a function.
Typically, you use a procedure to perform an action and a function to compute and return a value.
A subprogram follows PL/SQL block structure; that is, it has:
■ Declarative part (optional)
The declarative part contains declarations of types, constants, variables, exceptions, explicit cursors, and
nested subprograms. These items are local to the subprogram and cease to exist when the subprogram
completes execution.
■ Executable part (required)
The executable part contains statements that assign values, control execution, and manipulate data.
■ Exception-handling part (optional)
The exception-handling part contains code that handles exceptions (run-time errors).
What are the different Block Types?
There are three types of blocks that make up a PL/SQL program:
Anonymous blocks: These are the unnamed PL/SQL blocks that are embedded within an application or
are issued interactively.
Procedures: These are the named PL/SQL blocks. These blocks accept inbound parameters but won't
explicitly return any value.
Functions: These are the named PL/SQL blocks. These blocks accept inbound parameters and will always
return a value. The structure of a function is like that of a procedure, except that it includes a RETURN
clause and at least one RETURN statement.
Typically, you use a procedure to perform an action and a function to compute and return a value.
What is a Stored SubProgram?
A stored subprogram is a subprogram that is stored in the database. Because they are stored in the
database, stored programs can be used as building blocks for many different database applications. (A
subprogram that is declared within another subprogram, or within an anonymous block, is called a
nested subprogram or local subprogram. It cannot be invoked from outside the subprogram or block in
which it is declared. An anonymous block is a block that is not stored in the database.)
There are two kinds of stored subprograms:
Standalone stored subprogram, which is created at schema level
Package subprogram, which is created inside a package
Standalone stored subprograms are useful for testing pieces of program logic, but when you are sure
that they work as intended, Oracle recommends that you put them into packages.
What are Packages?
A package is a PL/SQL unit that consists of related subprograms and the explicit cursors and variables
that they use.
Oracle recommends that you put your subprograms into packages. Some of the reasons are:
Packages allow you to hide implementation details from client programs.
Package subprograms must be qualified with package names when invoked, which ensures that their
names will always work.
Package subprograms can send and receive records and collections.
What is a Collection?
A collection is a PL/SQL composite variable that stores elements of the same type in a specified order,
similar to a one-dimensional array. The internal components of a collection are called elements. Each
element has a unique subscript that identifies its position in the collection.
To access a collection element, you use subscript notation:
collection_name(element_subscript).
You can treat collection elements like scalar variables. You can also pass entire collections as
subprogram parameters (if neither the sending nor receiving subprogram is a standalone stored
subprogram).
A collection method is a built-in PL/SQL subprogram that either returns information about a collection
or operates on a collection. To invoke a collection method, you use dot notation:
collection_name.method_name.
For example, collection_name.COUNT returns the number of elements in the collection.
PL/SQL has three types of collections:
■ Associative arrays (formerly called "PL/SQL tables" or "index-by tables")
■ Nested tables
■ Variable arrays (varrays)
What is a Trigger?
While working with a database application, you may want to add programmatic functionality that
executes when specific operations occur in the database. For example, there may be typical scenarios
such as the following:
Example 1: You may want to insert data into a table. You find that the new data is inconsistent with the
existing data in the table. You may want the system to raise an error that will cause the transaction to
be rolled back.
Another example is: You may want the system to record information such as the timing and the details
of the user modifying data in a table.
In such scenarios, Triggers help the user deal with these and other complex situations. A trigger is a
PL/SQL unit that is stored in the database and (if it is in the enabled state) automatically executes
("fires") in response to a specified event.
What are the uses of a Trigger?
One use of triggers is to enforce business rules that apply to all client applications. For example, suppose
that data added to the EMPLOYEES table must have a certain format, and that many client applications
can add data to this table. A trigger on the table can ensure the proper format of all data added to it.
Because the trigger executes whenever any client adds data to the table, no client can circumvent the
rules, and the code that enforces the rules can be stored and maintained only in the trigger, rather than
in every client application.
You can use triggers for:
• Improving data security i.e. Triggers provide enhanced and complex security checks and auditing.
• Improving data integrity where Triggers enforce dynamic data integrity and complex referential
integrity constraints.
Triggers ensure that related operations are performed together implicitly
Slide 6: Moving on, the next topic in this course is about Creating Standalone Stored Sub Programs and
Packages.
Slide 7: Overview- Standalone Stored Sub Programs and Packages
Introduction: A PL/SQL program comprises one or more blocks. These blocks can be entirely
separate or nested within another.
In this topic, we discuss what Standalone SubPrograms and Packages are.
Overview: A subprogram is a PL/SQL unit that consists of SQL and PL/SQL statements that solve a
specific problem or perform a set of related tasks. A stored subprogram is a subprogram that is stored in
the database. Because they are stored in the database, stored programs can be used as building blocks
for many different database applications.
Anonymous Blocks: are the unnamed PL/SQL blocks that are embedded within an application or are
issued interactively.
Procedures: The structure of a Procedure follows a PL/SQL block structure and these blocks accept
inbound parameters but do not explicitly return any value.
Functions: Functions are a kind of Stored Subprogram whose structure is like that of a procedure,
except that it includes a RETURN clause and at least one RETURN statement.
Packages: A Package is an encapsulated collection of related program objects which are stored together
in the database.
Program objects include procedures, functions, variables, constants, cursors, and exceptions.
Slide 8: Anonymous Blocks
Features of an Anonymous Block :
Let us look at the features of Anonymous Blocks. As we know, Anonymous blocks are unnamed blocks.
They are declared inline at the point in an application where they are to be executed and are compiled
each time the application is executed.
Anonymous blocks are not stored in the database, and they are passed to the PL/SQL engine for
execution at run time.
You will not be able to invoke or call the block that you wrote earlier because blocks are anonymous and
do not exist after they are executed.
Anonymous blocks can serve as nested blocks inside procedures, functions, and other anonymous
blocks.
Structure of an Anonymous Block:
The structure of an Anonymous Block is as shown. Here, it has three basic parts: a declarative part
as(DECLARE), an executable part (from BEGIN through END), and an exception-handling (EXCEPTION)
part that handles error conditions. Only the executable part is required. The optional declarative part is
written first, where you define types, variables, and similar items. These items are manipulated in the
executable part. Exceptions raised during execution can be dealt with in the exception-handling part.
Slide 9: Demo Setup
Following is a demonstration about Creating an Anonymous Block
Slide 11: About Procedures
Structure of a Procedure
In this topic, we discuss about Procedures. First, let us take a look at the Structure of a Procedure.
The structure of a Procedure is as shown
The code that begins with PROCEDURE and ends before IS or AS is the subprogram signature. The
declarative, executable, and exception-handling parts comprise the subprogram body.
Creating and Managing Procedures:
You create new procedures with the CREATE PROCEDURE statement, which may declare a list of
parameters and must define the actions to be performed by the standard PL/SQL block. The CREATE
clause enables you to create stand-alone procedures that are stored in an Oracle database.
To create a standalone stored procedure, use either the SQL Developer tool Create PL/SQL Procedure or
the DDL statement CREATE PROCEDURE.
To change a standalone stored Procedure, use either the SQL Developer tool Edit or the DDL statement
ALTER PROCEDURE
To drop a standalone stored procedure, use either the SQL Developer navigation frame and Drop tool,
or the DDL statement DROP PROCEDURE
Using Parameters
Parameters are used to transfer data values between the calling environment and the procedure (or
subprogram). Parameters are also known as arguments. Parameters are declared in the subprogram
header, after the name and before the declaration section for local variables.
Parameters are subject to one of the three parameter-passing modes: IN, OUT, and IN OUT.
An IN parameter passes a constant value from the calling environment to the procedure.
An OUT parameter passes a value from the procedure to the calling environment.
An IN OUT parameter passes a value from the calling environment to the procedure and a possibly
different value from the procedure back to the calling environment using the same parameter.
Slide 12: Following is a demonstration about Creating a Standalone Stored Procedure
Slide 14: About Functions
Structure of a Standalone Stored Function:
In this topic, we discuss about Functions. A function is a named PL/SQL block that can accept
parameters, be invoked, and return a value. In general, you use a function to compute a value.
The structure of a function is as shown:
The structure of a function is like that of a procedure, except that it includes a RETURN clause and at
least one RETURN statement.
An example of using a Function is shown in the image below
In this example, the get_sal function is created with a single input parameter and returns the salary as a
number.
The get_sal function returns the common programming practice of assigning a returning value to a local
variable and uses a single RETURN statement in the executable section of the code to return the value
stored in the local variable. If your function has an exception section, then it may also contain a RETURN
statement.
Invoke a function as part of a PL/SQL expression, because the function will return a value to the calling
environment, such as Oracle Application Express (formerly HTML DB). The second code box uses the
EXECUTE command to call the DBMS_OUTPUT.PUT_LINE procedure, whose argument is the return value
from the function get_sal. In this case, get_sal is invoked first to calculate the salary of the employee
with ID 100. The salary value returned is supplied as the value of the DBMS_OUTPUT.PUT_LINE
parameter which displays the result.
Creating and Managing Functions:
To create a standalone stored function, you can use either the SQL Developer tool Create PL/SQL
Function or the DDL statement CREATE FUNCTION.
To change a standalone stored function, use either the SQL Developer tool Edit or the DDL statement
ALTER FUNCTION
To drop a standalone stored function, use either the SQL Developer navigation frame and Drop tool, or
the DDL statement DROP FUNCTION.
Slide 15: Demo Setup
Following is a step by step method of Creating a Standalone Stored Function which allows you to
perform certain tasks for Creating a Function based on certain instructions given to you. This
demonstration is silent.
Slide 17: About Packages
Package Structure:
This topic discusses about packages
A package always has a specification, and it usually has a body
The package specification defines the package, declaring the types, variables, constants, exceptions,
explicit cursors, and subprograms that can be referenced from outside the package. A package
specification is an application program interface (API): It has all the information that client programs
need to invoke its subprograms, but no information about their implementation.
The package body defines the queries for the explicit cursors, and the code for the subprograms, that
are declared in the package specification (therefore, a package with neither explicit cursors nor
subprograms does not need a body). The package body can also define local subprograms, which are not
declared in the specification and can be invoked only by other subprograms in the package. Package
body contents are hidden from client programs. You can change the package body without invalidating
the applications that call the package.
Creating and managing Packages:
To create a package specification, use either the SQL Developer tool Create PL/SQL Package or the DDL
statement CREATE PACKAGE.
To change a package specification, use either the SQL Developer tool Edit or the DDL statement CREATE
PACKAGE with the OR REPLACE clause.
To create a package body, use either the SQL Developer tool Create Body or the DDL statement CREATE
PACKAGE BODY.
To drop a package (specification and body), use either the SQL Developer navigation frame and Drop
tool, or the DDL statement DROP PACKAGE.
Slide 18: Demo setup
Following is a demonstration about Creating a Package in PL/SQL
Slide 20: Review
Let us now take a brief pause by taking a quiz
Slide 22: Road Map
The next topic is about Controlling the Program Flow in PL/SQL
Slide 23: Control Program Flow
Overview: In this topic, we discuss about Controlling Program Flow using control statements.
Unlike SQL, which runs statements in the order in which you enter them, PL/SQL has control statements
that let you control the flow of your program
PL/SQL has three categories of control statements: They are- Conditional selection statements, Loop
statements and Sequential Control Statements
■ Conditional selection statements, let you execute different statements for different data values.
The conditional selection statements are IF and and CASE.
■ Loop statements, let you repeat the same statements with a series of different data values.
The loop statements are FOR LOOP, WHILE LOOP and basic LOOP.
The EXIT statement transfers control to the end of a loop. The CONTINUE statement exits the current
iteration of a loop and transfers control to the next iteration. Both EXIT and CONTINUE have an optional
WHEN clause, in which you can specify a condition.
■ Sequential control statements, let you go to a specified, labeled statement, or to do nothing.
The sequential control statements are GOTO and and NULL.
Using the IF Statement:
The IF statement either executes or skips a sequence of statements, depending on the value of a
Boolean expression.
The IF statement has this syntax as shown:
For example, a company evaluates employees twice a year in the first 10 years of employment, but only
once a year afterward. You can write a function that returns the evaluation frequency for an employee
using an IF statement to determine the return value of the function. Click on the image to view the code.
Using the CASE Statement:
The CASE statement chooses from a sequence of conditions, and executes the corresponding statement.
The simple CASE statement evaluates a single expression and compares it to several potential values. It
has this syntax as shown:
The searched CASE statement evaluates multiple Boolean expressions and chooses the first one whose
value is TRUE.
For example, In a company, an employee is evaluated only once a year. But, you might want to use the
eval_frequency function to suggest a salary increase, which depends on the JOB_ID. You can use a CASE
statement in the function to do this. Click on the image to view the function using a CASE statement.
Using the FOR LOOP statement:
The FOR LOOP statement repeats a sequence of statements once for each integer in the range
lower_bound through upper_bound.
The syntax is as shown
The statements between LOOP and END LOOP can use counter, but cannot change its value.
In the same example as before, Instead of a salary increase, you might want the eval_frequency function
to report what the salary would be if it increased by the suggested amount every year for five years. You
can enhance the function using a For Loop. Click on the image to view the example.
Using the WHILE LOOP:
The WHILE LOOP statement repeats a sequence of statements while a condition is TRUE.
The syntax is as shown:
Suppose that the eval_frequency function uses the WHILE LOOP statement instead of the FOR LOOP
statement, and ends after the proposed salary exceeds the maximum salary for the JOB_ID. you can
change the eval_frequency function as shown in the example. Click on the image to view the example.
Using the BASIC LOOP and EXIT WHEN statements:
The basic LOOP statement repeats a sequence of statements. Its syntax is as shown:
At least one statement must be an EXIT statement; otherwise, the LOOP statement runs indefinitely.
The EXIT WHEN statement (the EXIT statement with its optional WHEN clause) exits a loop when a
condition is TRUE and transfers control to the end of the loop.
In the eval_frequency function, in the last iteration of the WHILE LOOP statement, the last computed
value usually exceeds the maximum salary. You can change the WHILE LOOP statement to a basic LOOP
statement that includes an EXIT WHEN statement, as shown in the example. Click on the image to view
the example.
Slide 24: Course Review
So, in the first part of this course, we talked about some basic PL/SQL concepts which included
•
Getting Familiar with the commonly used terms in PL/SQL
•
Creating Standalone Stored Sub Programs and Packages
•
Getting Familiar with Controlling the Program Flow in PL/SQL
Well, we have now completed the first part. Please refer to the second part to complete this course.
Thank you!