RDBMS Conceptss

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RDBMS Concepts


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Database

Database is an organized collection of data.

Collection ofrecords stored in a systematic way.

Organized for Better Retrieval and Sorting.
http://en.wikipedia.org/wiki/Database_recordhttp://en.wikipedia.org/wiki/Database_record


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Types of Database Models

Hierarchical model - Data is organized into a tree-like

structure

Network model - Uses recordsand sets. Records contain

fields, sets define man-many relationships.

Relational model Geared for OLTP

Dimensional Model Geared for Datawarehousing

Object Relational Model Object Oriented Features


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Basic Constructs

Tables

Columns

Constraints

Indexes

Views

Procedures

SQL


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Table & Columns

In a relational database and SQL databases a table is a set of

data elements (values) that is organized using a model ofhorizontal rows and vertical columns.

Columns form the attributes of a table. A table consists of

one or more columns. Every RDBMS has a restriction on themax columns.

Eg: Oracle allows 1000 columns per table
http://en.wikipedia.org/wiki/Relational_databasehttp://en.wikipedia.org/wiki/SQL_databasehttp://en.wikipedia.org/wiki/Row_%28database%29http://en.wikipedia.org/wiki/Column_%28database%29http://en.wikipedia.org/wiki/Column_%28database%29http://en.wikipedia.org/wiki/Row_%28database%29http://en.wikipedia.org/wiki/SQL_databasehttp://en.wikipedia.org/wiki/Relational_database


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Primary Key

Primary key is a value that can be used to identify a unique

row in a table.

Primary key is a candidate key chosen as the main method of

uniquely identifying a tuple in a relation.

Natural Key Key as understood by Business Eg: Associate

Id

Surrogate Key Non Business Key Eg : Sequence Number


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Primary Key..

Should be immutable, its value should not be changed

during the course of normal operations of the database.

Candidate keys uniquely identifying a row but are likely not

to be immutable.

Primary key should generally be short to minimize data

stored by relations.

Can be a compound consisting on multiple columns.


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Foreign Keys

A field or group of fields that point to a key field or group of

fields usually in a different table.

In scenarios where a foreign key refers to the same table

itself it is a self key.

Ensures Data Integrity

Eg : Employee Belonging to a Department


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Foreign Keys Example

ASSOCIATE ID

FIRST NAME

LAST NAME

DEPT NO

EmployeeDEPT NO

DEPT NAME

Department


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Not Nul ls


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Constraint - Not Nul l

Enforces the need for data to be mandatory.

Applied at column level.

Record cannot be created if value is not supplied.

Eg: First Name is mandatory.


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Constraint - Check

Enforces the values entered are from a fixed List of Values.

Valid only when a fixed list is present and action is more for

validation.

For variable list a Master Detail with Foreign Keys must be

used.

Eg: A flag indicating the gender M or F.


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Defaults

Provides for a default value when none is provided.

Useful when user wants to avoid specifying a value every

time.

Eg: Default the date to todays date.


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Defaults


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I ndexes

Feature in a database that allows quick access to the rows in

a table.

Smaller than the original table.

Optimized for quick searching.

Eg : Search on the name of an associate


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SQL Select

Structured Query Language

Way to access data.

Uses simplified English

SQL is a database access, nonprocedural language. Users describe

in SQL what they want done, and the SQL language compiler

automatically generates a procedure to navigate the database andperform the desired task.

Eg: Get all the employess

Select * from emplo yee


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SQL Select.

Get all employees whose salary > 5000

Select * from employee where salary > 5000

Get associate id and first name

Select associate_id,first_name from employee


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Samples of Select


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SQL Standards

ANSI SQL

The American National Standards Institute (ANSI) has

established a set of industry standards for SQL.

Set of standards which SQL language must be complainant

with.

Database vendors introduce non ANSI complaint features.

Reduction in portability due to non-compliance.


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SQL Joins

Combines records from two or more tables in a relational

database.


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Cross Join

A cross join returns the cartesian product of the sets of rows fromthe joined tables.

While not used commonly, a cross join is the foundation uponwhich inner joins are built.

SELECT *

FROM emplo yee CROSS JOIN departm ent;

SELECT *

FROM emplo yee,department;


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I nner Join

Intersection between the two tables

SELECT * FROM emplo yee ,departmen tWHERE emp loy ee.DepartmentID = departm ent.Departm entID

L ft t j i


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Left outer join

Instead of limiting results to those in both tables, it limits

results to those in the "left" table

SELECT * FROM employee LEFT OUTER JOIN department ON

employee.DepartmentID = department.DepartmentID

Ri ht t j i


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Right outer join

Much like a left outer join, except that the tables are reversed

SELECT * FROM emp loy ee RIGHT OUTER JOIN departm ent ON

emp loy ee.DepartmentID = department.Departm entID

F ll t j i


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Ful l outer join

Combines the results of both left and right outer joins.

SELECT * FROM employ ee FULL OUTER JOIN department ON

emp loy ee.DepartmentID = department.Departm entID


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SQL I nserts

Adds a record to a table in a relational database.

INSERT INTO table (column1, [co lum n2, ... ]) VALUES (value1,

[value2, ...])

Eg: INSERT INTO phone_book (name, number) VALUES ('JohnDoe', '555-1212');


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SQL Updates

Updates an existing record from a table in a relational

database.

Eg: Update phone_book set name = John Davis where name

='John Doe';


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SQL Delete

Deletes an existing record from a table in a relational

database.

Eg: Delete phone_book where name = John Davis


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Commit/Rollback

Signifies the end of a transaction unit.

Commit Means finalize and write all these changes to the

database.

Rollback Revert back all changes made to the database.

Valid from the point when the last commit/rollback was

issued.


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Transaction


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SQL Types

DML Data Manipulation Language

Changes to Data

Eg: Selec t, Ins ert, Upd ate, Delete

DDL

Data Definition Language

Changes to structure

Eg: Create Table


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Sample Create Table

CREATE TABLE EMP

(

EMPNO NUMBER(9),

ENAME VARCHAR2(10 BYTE),

JOB VARCHAR2(9 BYTE),

MGR NUMBER(4),

HIREDATE DATE,

SAL NUMBER(7,2),

COMM NUMBER(7,2),

DEPTNO NUMBER(2) );

CREATE UNIQUE INDEX PK_EMP ON EMP

(EMPNO);

ALTER TABLE EMP ADD (

CONSTRAINT PK_EMP PRIMARY KEY (EMPNO));

ALTER TABLE EMP ADD (

CONSTRAINT FK_DEPTNO FOREIGN KEY (DEPTNO)

REFERENCES DEPT (DEPTNO));


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Triggers

Applicable to a table. Way to enforce complex integrity rules

which cannot be implemented by constraints.

Consists of a SQL statements along with procedural

constructs.

Get fired when the relevant condition is met, irrespective of

the source of the transaction.


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Stored Procedures

A procedure orfunction is a object that consists of a set of

SQL statements, grouped together, stored in the database

Contains business logic and/or complex logic which cannot

be done by simple SQL

Procedures and functions let you combine the ease and

flexibility of SQL with the procedural functionality of a

structured programming language.


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Views

Tailored presentation of the data contained in one or more

tables or other views.

Can be thought of as a stored query or a virtual table.

Eg: The emp loyees table has several co lumns and num erous

rows of information. If you want users to see only f ive of these

colum ns or on ly speci f ic rows, then yo u can create a view of

that table.


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Sample View


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Security

Schema Level Security Login

Object Level Security Tables, Views etc


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ACID

Refers to Atomicity, Consistency, Isolation and Durability.

Key properties of any DBMS without which integrity of the

database cannot be guaranteed.

Terms relevant to wrt a Transaction

Transaction is a single logical operation

Eg : Transfer of Funds (con sists o f mu l t ip le steps)

A i i


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Atomicity

Guarantee that either all of the tasks of a transaction are

performed or none of them are.

Transfer of funds can be completed or it can fail for a

multitude of reasons, but atomicity guarantees that one

account won't be debited if the other is not credited as well.

C i t


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Consistency

Database maintains it state when the transaction begins and

when it ends.

Transaction cannot break the rules, orin tegr i ty con straints,

of the database.

If an integrity constraint states that all accounts must have a

positive balance, then any transaction violating this rule will

be aborted.

I l ti


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Isolation

Ability to make operations in a transaction appear isolated

from all other operations.

No operation outside the transaction can ever see the data in

an intermediate state.

Transferred funds can be seen on one account or the other,

but never on botheven if the query runs while the transfer

was still being processed.

D bilit


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Durability

Guarantee that once the user has been notified of success,

the transaction will persist, and not be undone.

It will survive system failure, the database has checked the

integrity constraints and won't need to abort the transaction.

A hit t O l


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ArchitectureOracle

P A hit t O l


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Process Architecture - Oracle

C D t b i M k t


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Common Databases in Market

Oracle

SQL Server

DB2

Teradata

Sybase

My SQL

G A i t


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Group Assignments

Gather Information On ..

Supplier

Current Release

Company Stability

Support Infrastructure

Cost Criteria

Operating System Support

Technical Features

Market Penetration

Group Presentations


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Group Presentations

General Information

Each Group will be required to give a 15-30 minute formal presentationon their chosen topic.

Except for software reviews all research MUST consist of at least three

sources and EVERY GROUP WILL PROVIDE A BIBLIOGRAPHY OF

THEIR REFERENCES at the time of presentation.

Include your thoughts throughout the presentation. NOT just a

short summation at the end.

Fully discuss topic. For example, do not try to discuss all of Oracle

Designer, take a part of it, like the Server Model, or ERD function.

For topics that fall under number 2 and 3, use your own personal

observations.

Group Presentations (2)


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Group Presentations (2)

Possible Topics

1. A subject scheduled to be discussed in class

2. Personal review of a database design tool such as Power Designer,Oracle Designer, ER-Win etc.

3. Review of a database system such as Oracle, Sybase, I nformix, etc.


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RDBMS Conceptss

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