DATABASE MANAGEMENT SYSTEMSCMAM301

Introduction to database management systems

What is Database?What is Database Systems?Types of Database.Database Management SystemElements of Database

database

a collection of information that is related to a particular subject or purpose.

DATABASE

A database is a collection of occurrence of multiple record types containing the relationship between records, data aggregate and data items. A database may also be defined as a collection of interrelated data stored together without harmful and unnecessary redundancy (duplicate data) to serve multiple applications.

DATABASE SYSTEM

Database System is an integrated collection of related files along with the detail about their definition, interpretation, manipulation and maintenance. It is a system, which satisfied the data need for various applications in an organization without unnecessary redundancy.

DATABASE SYSTEM

A database system is based on the data. Also a database system can be run or executed by using software called DBMS (Database Management System). A database system controls the data from unauthorized access.

FOUNDATION OF DATA

1. Character2. Field3. Record4. File5. Database

character

It is the most basic logical data element. It consists of a single alphabetic, numeric, or other symbol.

field

It consists of a grouping of characters. A data field represents an attribute (a characteristic or quality) of some entity (object, person, place, or event).

record

The related fields of data are grouped to form a record. Thus, a record represents a collection of attributes that describe an entity. Fixed-length records contain, a fixed number of fixed-length data fields. Variable-length records contain a variable number of fields and field lengths.

File

A group of related records is known as a data file, or table. Files are frequently classified by the application for which they are primarily used, such as a payroll file or an inventory file, or the type of data they contain, such as a document file or a graphical image file. Files are also classified by their permanence, for example, a master file versus a transaction file. A transaction file would contain records of all transactions occurring during a period, whereas a master file contains all the permanent records. A history file is an obsolete transaction or master file retained for backup purposes or for long-term historical storage called archival storage.

Database

It is an integrated collection of logically related records or objects. A database consolidates records previously stored in separate files into a common pool of data records that provides data for many applications. The data stored in a database is independent of the application programs using it and of the type of secondary storage devices on which it is stored.

TYPES OF DATABASE

1. Operational Databases2. Distributed Databases3. External Databases4. Hypermedia Databases

Operational Databases

The databases store detailed data needed to support the operations of the entire organization. They are also called subject area databases (SADB), transaction databases, and production databases: Examples are customer databases, personnel databases, inventory databases, and other databases containing data generated by business operations.

Distributed Databases

Many organizations replicate and distribute copies or parts of databases to network sewers at a variety of sites. These distributed databases can reside on network servers on the World Wide Web, on corporate Intranets or extranets, or on other company networks. Distributed databases may be copies of operational or analytical. databases, hypermedia or discussion databases, or any other type of database. Replication and distribution of databases is done to improve database performance and security.

External Databases

Access to external, privately owned online databases or data banks is available for a fee to end users and organizations from commercial online services, and with or without charge from many sources on the Internet, especially the Web.

Hypermedia Databases

It consists of hyperlinked pages of multimedia (text, graphics, and photographic images, video clips, audio segments, etc.). From a database management point of view, the set of interconnected multimedia pages at a website is a database of interrelated hypermedia page elements, rather than interrelated data records.

DATABASE MANAGEMENT SYSTEM

A DBMS is best described as a collection of programs that manage the database structure and that control shared access to the data in the database. Current DBMSes also store the relationships between the database components; they also take care of defining the required access paths to those components.

DATABASE MANAGEMENT SYSTEM

A database management system (DBMS) is the combination of data, hardware, software and users to help an enterprise manage its operational data.

The main function of a DBMS is to provide efficient and reliable methods of data retrieval to many users. Efficient data retrieval is an essential function of database systems. DBMS must be able to deal with several users who try to simultaneously access several items and most frequently, the same data item A DBMS is a set of programs that is used to store and manipulation.

Examining the DATABASE Environment

Database Objects Objects are the structures you create and methods you employ to maintain and display your data

Examining the DATABASE EnvironmentTables Hold all data in the database Are two dimensional and have rows and columns Store related data in rows (records) and columns

(fields) Row ordering is unimportant, as the rows can be

sorted and rearranged and not change the fundamental table information

Column ordering is unimportant, meaning that the particular ordering of the columns bear no significance, and any table column may be placed in any particular position

Examining the DATABASE EnvironmentFORMS Are custom screens that provide an

easy way to enter and view data in a table.

Provide a way to view table data one row at a time

Facilitate data entry for inexperienced users

Display data from tables or queries but do not actually hold data

Examining the DATABASE EnvironmentQUERIES View, filter, calculate, change, sort, and

examine the data stored in tables Database supports several types of queries

classified as either action queries or selection queries. Select queries are the most common type.

Subsets of rows are returned when selection criteria are specified to filter the data.

Example of QUERY

”SELECT CardCode, CardName, Address FROM OCRD”

Examining the DATABASE EnvironmentREPORTS Present data from a table or query in a

printed format Provide formatted, hard-copy output. Display database information that can be

supplied by tables, queries, or both. Can be customized to produce typeset-level

output

Elements of database

TABLES store data within the database

QUERIES pull out specific dataFORMS make it easy to put data

into tablesREPORTS put data in an easily-read

format