Oracle SQL Basics

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2011

ANKURRAINA

[ORACLE DATABASE

PRESENTATION FOR THE

BASIC SQL UNDERSTANDING]All the rights are reserved with the author. No part of this publication may be changed in any form

without the prior permission of the author. Copyright 2011


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ANKUR RAINA 09-IT-4505

CONTENTS

1. Introduction to Oracle RDBMS 3

1.1.Features 3

1.2.Oracle Internet Platform 4

2. E.F.Codds Rules 5

2.1 Rules 5

2.2 Satisfied by Oracle RDBMS 6

3. Oracle Database Architecture 8

3.1. The Database 9

3.2. The Instance 11

4. SQL Statements 14

4.1.Types 14

4.2. Capabilities of SQL SELECT Statements 15

4.3.Data Retrieval UsingSELECT Statement 15

4.4.Defining aNULL value 16

4.5.Defining a Column Alias 17

4.6.Restricting and Sorting Statements 17

5. Using Single Row Functions To Customize Output 18

5.1. Features 22

5.2. General Functions 22

5.3. CASE Expression 24

5.4. DECODE Function 25

6. Reporting Aggregating Data Using Group Functions 26

6.1. Group Function 266.2. Creating Groups of Data: GROUP BY clause syntax 27

6.3. Using GROUP BY clause for multiple columns 28

6.4. Restricting Group Results by HAVING clause 28

7. Displaying Data From Multiple Tables 29

7.1 Using Subqueries to Solve Queries 30


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8. Manipulating Data 31

8.1. INSERT statement 31

8.2. UPDATE statement 32

8.3. DELETE statement 328.4. TRUNCATE statement 32

9. Database Objects 34

9.1. CREATE statement 34

9.2. CREATE TABLE using a sub-query 35

9.3. Dropping a table 35

10.Creating Other Schema Objects 36

10.1. Views 36

10.2.Creating views 36

10.3.Sequence 37

10.4.Indexes 37

10.5.Synonyms 38

11.References 39


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CHAPTER 1

Our goal is very simply to become the desktop for e-businesses - Larry Ellison

Introduction to Oracle RDBMS

The Oracle Database (commonly referred to as Oracle RDBMS or simply as Oracle) is an

object-relational database management system (ORDBMS) produced and marketed by

Oracle Corporation. Larry Ellison and his friends and former co-workers Bob Miner and Ed

Oates started the consultancy Software Development Laboratories (SDL) in 1977. SDL

developed the original version of the Oracle software. The name Oracle comes from the

code-name of a CIA-funded project Ellison had worked on while previously employed by

Ampex. The latest release of Oracle RDBMS is 11g Release 2.

Features:-


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Oracle Internet Platform

The Oracle products provide all the necessary components to develop an application.The integrated Oracle Internet Platform includes everything needed to develop,

deploy, and manage internet applications, including these three core pieces:

1. Browser-based clients to process presentation

2. Application servers to execute business logic and serve presentation logic to

browser-based clients

3. Databases to execute database-intensive business logic and serve data


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CHAPTER 2

E.F.Codds Rules

E.F. Codd, the famous mathematician has introduced 12 rules for the relational model for

databases commonly known as Codd's rules. The rules mainly define what is required for a

DBMS for it to be considered relational, i.e., an RDBMS. There is also one more rule i.e.

Rule00 which specifies the relational model should use the relational way to manage the

database. The rules and their description are as follows:-

Rules:

Rule 000: Zeroth rule:

An RDBMS system should be capable of using its relationalfacilities (exclusively) to manage

the database.

Rule 1: The information rule:

All information in the database is to be represented in one and only one way. This is

achieved by values in column positions within rows of tables.

Rule 2: The guaranteed access rule:

All data must be accessible with no ambiguity. This is achieved in the RDBMS by using the

primary key concept.

Rule 3: Systematic treatment of null values:

The DBMS must allow each field to remain null. The null can be stored in any field of any

datatype.

Rule 4: Active online catalog based on the relational model:

The authorized users can access the database structure by using common language i.e. SQL.

Rule 5: The comprehensive data sublanguage rule:

The system must support at least one relational language that has simple syntax and

transaction management facilities. It can be used in the application as well as in the RDBMS

systems.


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Rule 6: The view updating rule:

All views must be updatable by the system.

Rule 7: High-level insert, update, and delete:

The system is able to insert, update and delete operations fully. It can also perform the

operations on multiple rows simultaneously.

Rule 8: Physical data independence:

Changes to the physical storage structure must not require a change to an application

based on the structure.

Rule 9: Logical data independence:

Changes to the logical level (tables, columns, rows, and so on) must not require a change to

an application based on the structure.

Rule 11: Distribution independence:

The distribution of portions of the database to various locations should be invisible to users

of the database.

Rule 12: The non- subversion rule:

If the system provides a low-level (record-at-a-time) interface, then that interface cannot be

used to subvert the system, for example, bypassing a relational security or integrity

constraint.

Note:-Any database management system which fulfills 6 or more than 6 rules can be

considered as the RDBMS.

Rules satisfied by Oracle RDBMS

Oracle RDBMS follows 11 out of 12 rules. One rule which is not followed is debatable.

1. View Updating Rule:

It is because, according to Dr. E.F.Codd, every view should support full range of data

manipulation, but in Oracle, it is not feasible for complex views based on multiple

tables.


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2. Systematic Treatment of Null value

Null in Oracle is treated as absence of a value or unknown status ( in case of

comparison of values ) and it does not have any systematic representation. In Oracle,

no two null values are equal (as this will return a value which is treated as unknown

by Oracle). If there is a systematic representation, then NULL value must becomparable.


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CHAPTER 3

Oracle Database Architecture

The Oracle RDBMS consists of two main components:-

1. The Database or the Physical Structures

2. The Instance or the Memory Structures

Control Files:

These files contain data about the database itself, called the metadata. These files are

critical to the database. Without them, one cannot open the data files to access the data

within the database.

Data Files:

These files contain the data of the database.


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Online Redo Log Files:

These files allow for instance recovery of the database. If the database were to crash and

not lose data files, the instance will be able to recover the database with the information in

these files.

Tablespaces and Data Files:


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A database is divided into logical storage units called tablespaces, which can be used to

group related logical structures. Each database is logically divided into one or more

tablespaces. One or more data files are explicitly created for each tablespace to physically

store the data of all logical structures in a tablespace.

Segments, Extents, and Blocks:

Database objects such as tables and indexes are stored in tablespaces as segments. Each

segment contains one or more extents. An extent consists of contiguous data blocks, which

means that each extent can exist only in one data file. Data blocks are the smallest units of

I/O in the database.

When the database requests a set of data blocks from the operating system (OS), the OS

maps this to the actual OS block on the storage device. Because of this, one needs not to be

aware of the physical address of any data in the database. This also means that a data file

can be striped and or mirrored on several disks.

The size of the data block can be set at database creation time. The default size of 8K is

adequate for more databases. If your database supports a data warehouse application that

has large tables and indexes, then a larger block may be beneficial. If your database

supports a transactional application where reads and writes are very random, then a smaller

block size may be beneficial. The maximum block size is dependent on the OS. The minimum

block size is 2K and should rarely (if ever) be used.

There are other files that are not officially part of the database, but are important to the

successful running of the database. These are:

Parameter File:

The parameter file is used to define how the instance will be configured when it starts up.


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Password File:

This file allows users to connect remotely to the database and perform administrative tasks.

Archive Log Files:

These files contain an ongoing history of the redo generated by the instance. These files

allow for database recovery. By using these files and a backup of the database, it is possible

to recover a lost file.

Oracle Instance Management

An Oracle Database server consists of an Oracle Database and an Oracle instance. An Oracle

instance consists of memory buffers known as the System Global Area (SGA) and

background processes.

The instance is idle (non-existent) until it is started. When the instance is started, an

initialization parameter file is read and the instance is configured accordingly.

After the instance is started and the database is opened, users can access the database.


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Oracle Memory Structures

The basic memory structures associated with an Oracle instance include:

System Global Area (SGA):

It is shared by all server and background processes.

Program Global Area (PGA):

It is private to each server and background process; there is one PGA for each process.

The SGA is a shared memory area that contains data and control information for the

instance. The SGA consists of the following data structures:

Database buffer cache: Caches blocks of data retrieved from the database.

Redo log buffer: Caches redo information (used for instance recovery) until it can be written

to the physical redo log files stored on disk.

Shared pool: Caches various constructs that can be shared among users.

Large pool: Is an optional area used for buffering large I/O requests.

Java pool: Is used for all session-specific Java code and data within the Java Virtual Machine(JVM).


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Stream pool: Is used by Oracle Streams.

When we start the instance by using Enterprise Manager or SQL*Plus, the memory allocated

for the SGA is displayed.

A PGA is a memory region that contains data and control information for each serverprocess. A server process services a clients requests. Each server process has its own

private PGA area that is created when the server process is started. Access to it is exclusive

to that is created when the server process is started. Access to it is exclusive to that server

process, and is read and written only by the oracle code acting on behalf of it.

The amount of PGA memory used and its content depends on whether the instance is

configured in shared mode. Generally, the PGA contains the following:

Private SQL area: Contains data such as bind information and run-time memory

structures. Each session that issues a SQL statement has a private SQL area.

Session memory: Is memory allocated to hold session variables and other information

related to the session.


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CHAPTER 4

SQL Statements

SQL stand for Structured Query Language. SQL has become the de-facto standard languageused for creating and querying relational databases. The SQL statements can be categorized

as:-

Types of SQL Statements:

Data Manipulation Language:

It constitutes those commands which are used to maintain & query a database, including

updating, inserting, modifying and querying data.

SELECT

INSERT

UPDATE

DELETE

MERGE

Data Definition Language:

It constitutes those commands which are used to define a database including creating,

altering and dropping tables and establishing constraints.

CREATE

ALTER

DROP

RENAMETRUNCATE

COMMENT

Data Control Language:

It controls a database and deals with the administrative privileges.

GRANT

REVOKE


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ANKUR RAINA

Transaction Control:

A discrete unit of work that

computer system is called a t

COMMIT

ROLLBACK

SAVEPOINT

Capabilities of SQL SELE

The three basic capabilities o

Projection: To choose the c

Selection: To choose the ro

used to restrict the rows that

Joining: To bring together d

between them.

Data Retrieval: Using SE

SELECT identifies the column

FROM identifies the table con

If all columns are of data in a

ust be completely processed or not process

ansaction. The following commands control

CT statements:

SELECT statements are:

olumns in a table that is returned by a query

s in a table that is returned by a query. Var

are retrieved.

ta that is stored in different tables by speci

ECT Statement:

to be displayed.

taining those columns.

table are to be listed, an asterisk (*) can be

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ed at all within a

the transactions.

.

ious criteria can be

ying the link

sed.


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ANKUR RAINA

Defining a NULL value:

A null is a value that is unavai

same as a zero. Columns of a

(NOT NULL and PRIMARY

. . .

Arithmetic expressions contai

. . .

lable, unassigned, unknown, or inapplicable.

y data type can contain nulls. However, so

KEY) prevent nulls from being used in the c

ning a null value evaluate to null.

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A null is not the

e constraints

olumn.


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Defining a Column Alias:

A column alias is used to rename a column heading. It is useful with calculations. It either

follows the column name or an optional AS keyword is used between the column name and

alias. If the alias name is case sensitive, enclose it in double-quotation marks.

Restricting Rows: UsingWHERE clause:

WHERE restricts the query to rows that meet a condition

Condition is composed of column names, expressions, constants, and a comparison operator.

Character Strings and Dates:

Character strings and date values are enclosed in single quotation marks. Character strings

are case sensitive, and date values are format sensitive. The default date format is

DD-MON-RR.


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Comparison Conditions:


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Logical Conditions:


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Rules of Precedence

Sorting Data:

Sort retrieved rows with the ORDER BY clause:

1. ASC: ascending order, default

2. DESC: descending order

The ORDER BY clause comes last in the SELECT statement.


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Using Substitution Variables:

Substitution variables are used to temporarily store values with a single-ampersand (&) and

double-ampersand (&&) substitution. Substitution variables are used to supplement the

following:

1. WHERE clause

2. ORDER BY clause

3. Column expressions

4. Table names

5. Entire SELECT statements

Use the double ampersand (&&) if you want to reuse the variable value without

prompting the user each time.


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CHAPTER 5

Using Single Row Functions to Customize Output:

Features:

1. Used to manipulate data items

2. Accept arguments and return one value

3. Act on each row that is returned

4. Return one result per row

5. May modify the data type

6. Can be nested

7. Accept arguments that can be a column or an expression

General Functions:

FUNCTION SYNTAX DESCRIPTION

NVL NVL(expr1,expr2)

Converts a null value to actual

value.

NVL2 NVL2(expr1,expr2,expr3)

I f expr1 is not null, NVL2

returns expr2. If expr1 is null,NVL2 returns expr3.

NULLIF

NULLIF(expr1,expr2)

Compares two expressions

and returns null if they are

equal; returns the first

expression if they are not

equal.

COALESCE COALESCE(expr1,expr2,...,exprn)

Returns the first non-null

expression in the expression

list.


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USING NVL:

USING NVL2:

USING NULLIF:

USING COALESCE:


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CASE Expression:

It facilitates conditional inquiries by doing the work of an IF-THEN_ELSE statement.


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DECODE Function:

It facilitates conditional inquiries by doing the work of a CASE expression or

IF-THEN-ELSE statement.


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CHAPTER 6

Reporting Aggregated Data Using Group Functions:

Group Functions:

Group functions operate on sets of rows to give one result per row.

Types of Group functions are:

FUNCTION SYNTAX DESCRIPTION

AVG AVG([DISTINCT|ALL]n) Average value of n, ignoring nullvalues.

COUNT COUNT({*|[DISTINCT|ALL]expr}) No. of rows where exprevaluates to something other

than null(count all selected

rows using * , including

duplicates and rows with nulls)

MAX MAX([DISTINCT|ALL]expr) Max value of expr ignoring nullvalues

MIN MIN([DISTINCT|ALL]expr) Min value of expr ignoring nullvalues

STDDEV STDDEV([DISTINCT|ALL]x) Standard deviation of n ignoringnull values

SUM SUM([DISTINCT|ALL]n) Sum values of n ignoring nullvalues

VARIANCE VARIANCE([DISTINCT|ALL]x) Variance of n ignoring nullvalues

COUNT (*) returns the number of rows in a table.


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COUNT (expr) returns the number of rows with non-null values for expr.

COUNT (DISTINCT expr) returns the number of distinct non-null values of expr.

Creating Groups of Data: GROUP BY Clause Syntax


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Using GROUP BY clause on multiple columns

Restricting Group Results with HAVING clause:

When you use the HAVING clause, the Oracle Server restricts groups as follows:

1. Rows are grouped

2. The group function is applied

3. Groups matching the HAVING clause are displayed.


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CHAPTER 7

Displaying Data Using Multiple Tables

Creating Natural Joins:

The NATURAL JOIN clause is based on all columns in the two tables that have the

same name. It selects rows from the two tables that have equal values in all matched

columns. If the columns having the same names have different data types, an error is

returned.

If several columns have the same names but the data types do not match, natural

join can be applied by using the USING clause to specify the columns that should

be used for an equijoin. Use the USING clause to match only one column when

more than one column matches. Table name or alias is not used in the referenced

columns.


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Using Sub-Queries to Solve Queries:

Sub-Query:

A query within a query is known as a sub-query. A sub-query executes once before

the main query. The result of sub-query is used by the main query.


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CHAPTER 8

Manipulating Data:

A Data Manipulation language (DML) statement is executed when you: Add new rows to a table

Modify existing rows in a table

Remove existing rows from a table

A transaction consists of a collection of DML statements that form a logical

unit of work.

INSERT Statement:

Syntax:

Implicit Method: omit the column from the column list.

Explicit Method: Specify the NULL keyword in values clause.

UPDATE Statement:

UPDATE statement is used to modify the existing rows in a table. More than one row can be

updated at a time (if required).


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DELETE Statement:

DELETE Statement is used to remove existing rows from a table.

If one omits the WHERE clause, all the rows from the table will be deleted.

TRUNCATE Statement:

The TRUNCATE Statement removes all rows from a table, leaving the table empty and the

table structure intact. It is a Data Definition Language (DDL) statement rather than a DML

statement; cannot easily be undone.


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CHAPTER 9

Database Objects:

CREATE Statement:


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CREATE TABLE using a Sub-Query:

Dropping a Table:

All data and structure in the table are deleted.

Any pending transactions are committed.

All indexes are dropped.

All constraints are dropped.

You cannot roll back the DROP TABLE statement.


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Creating Other Schema Objects:

Views:

To restrict data access.

To make complex queries easy.

To provide data independence.

To present different views of the same data.

CREATE VIEWSyntax (simple view):

CREATE VIEW(complex view):


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You cannot modify data in a view if it contains:

Group functions

A GROUP BY clause

TheDISTINCT

keyword

The pseudo column ROWNUM keyword

Columns defined by expressions

You cannot add data in a view if following conditions along with conditions above prevail:

NOT NULL columns in the base tables that are not selected by the view.

Sequences:

A sequence

Can automatically generate unique numbers

Is a sharable object

Can be used to create a primary key value

Replaces application code

Speeds up the efficiency of accessing sequence values when cached in memory

Indexes:

An index:

Is a schema object

Can be used by the Oracle server to speed up the retrieval of rows by using a pointer

Can reduce disk I/O by using a path access method to locate data quickly

Is independent of the table that it indexes Is used and maintained automatically by the Oracle server


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Indexes are created in the following two ways:

Automatically: A unique index is created automatically when you define a PRIMARY

KEY or UNIQUE constraint in a table definition.

Manually: Users can create non-unique indexes on columns to speed up access to

the rows.

Syntax:

Synonyms:

Simplify access to objects by creating a synonym (another name for an object). With

synonyms, we can:

Create an easier reference to a table that is owned by another user

Shorten lengthy object names


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REFERENCES

Web Resources

http://wiki.answers.com/Q/What_are_EF_Codd_rules

www.oracle.com

www.wikipedia.com

www.oraclecoach.com

Books:

Study material by Oracle UniversityPress

Modern Database Management by JeffreyA. Hoffer, Mary B. Prescott and FredR. McFadden

Oracle SQL Basics

Documents

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