Show Database technology eliminates many of the problems of traditional file organization by organizing data: centralizing data and controlling redundant data, and serve many applications and different groups at the same time. A database management system (DBMS) is software that:
A relational DBMS, such as Microsoft Sequel Server or MYSQL, represents data as two-dimensional tables called relations. Each table consists of a grid of columns and rows of data. Each row is a record, or tuple, divided by columns into separate fields for that record. One column in each table acts as a primary key, defining for each record a key field that is used to uniquely identify each record. Relational databases use primary keys to connect records from one table to other tables. When a primary key from one table is used in second table to locate, or look-up, records from the first table, it is called a foreign key. Figure 6-4
In a relational database, three operations are used to develop sets of data:
Older, less flexible types of database systems include hierarchical DBMS, which model one-to-many relationships, and network DBMS, which model many-to-many relationships. Hierarchical and network Relational DBMS are suited for handling data, not graphics or multimedia. An object-oriented DBMS (OODBMS) stores the data and procedures that act on those data as objects that can be automatically retrieved and shared, and can manage multimedia and java applets. However, OODBMS are slower in handling large numbers of transactions. Hybrid object-relational DBMS systems are now available to provide capabilities of both object-oriented and relational DBMS. A DBMS includes capabilities and tools for accessing and managing data in a database, including:
Figure 6-6, Figure 6-7, Figure 6-8
A DBMS may also include capabilities for generating customized reports and developing desktop system applications. Considerations in designing a database include its:
Normalization is the process of creating small, stable, yet flexible and adaptive data structures from complex groups of data and minimizes repeated data groups. Figure 6-9, Figure 6-10
An entity-relationship diagram is used to diagram a data model and describe the relationships between different groups of data in the system. Without an appropriate data model for its databases, a database system will not be able to serve a business effectively. Figure 6-11
Database design also considers how the data are to be distributed, with a centralized database or with a distributed database (data that is stored in more than one physical location). There are two main methods of distributing a database: Partitioned: Different parts of the database are stored in separate locations Replicated: The database is duplicated at all locations Figure 6-12
Distributed systems:
What is database approach and filedatabase approach: allows the management of large amounts of organizational information. database management software: a powerful software tool that allows you to store, manipulate and retrieve data in a variety of ways. file-based system: an application program designed to manipulate data files.
What is flat data model in DBMS?A flat database refers to a simple DB system in which each database has to be represented as a single table, with all records saved as single rows of data separated by tabs or commas. A simple text file is typically used to store and physically display the table.
What is a difference between databases and flat file systems?Database provide more flexibility whereas flat file provide less flexibility. Database system provide data consistency whereas flat file can not provide data consistency. Database is more secure over flat files. Database support DML and DDL whereas flat files can not support these.
What are the two approaches for database management?There are two approaches for developing any database, the top-down method and the bottom-up method. While these approaches appear radically different, they share the common goal of uniting a system by describing all of the interaction between the processes.
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