DATABASE MANAGEMENT SYSTEMS CMAM301. Introduction to database management systems What is Database? What is Database Systems? Types of Database. Database. - презентация

1 DATABASE MANAGEMENT SYSTEMS CMAM301

2 Introduction to database management systems What is Database? What is Database Systems? Types of Database. Database Management System Elements of Database

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

4 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.

5 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.

6 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.

7 FOUNDATION OF DATA 1. Character 2. Field 3. Record 4. File 5. Database

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

9 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).

10 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.

11 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.

12 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.

13 TYPES OF DATABASE 1. Operational Databases 2. Distributed Databases 3. External Databases 4. Hypermedia Databases

14 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.

15 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.

16 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.

17 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.

18 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.

19 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.

20 Examining the DATABASE Environment Database Objects Objects are the structures you create and methods you employ to maintain and display your data

21 Examining the DATABASE Environment Tables 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

22 Examining the DATABASE Environment FORMS 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

23 Examining the DATABASE Environment QUERIES 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.

24 Example of QUERY SELECT CardCode, CardName, Address FROM OCRD

25 Examining the DATABASE Environment REPORTS 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

26 Elements of database TABLES store data within the database QUERIES pull out specific data FORMS make it easy to put data into tables REPORTS put data in an easily-read format