Database Management Systems: Database Management Systems What do you understand by Database Management System? What are its objectives? Discuss the various elements of Database System. : What do you understand by Database Management System? What are its objectives? Discuss the various elements of Database System. A database management system is a collection of interrelated data and a set of program to access those data. The collection of data, usually referred to as the "Database” contains information relevant to an enterprise. The primary goal of a DBMS is to provide a way to store and retrieve database information that is both convenient and efficient. PowerPoint Presentation: Database : An organization must have accurate and reliable data for effective decision making. For this, the organization maintains records of various facts of its operation by building appropriate models of the diverse classes of objects of interest. The models capture the essential properties of the objects and records relationship among them. Such related data is called “Database ” Objectives :DBMS : Objectives :DBMS i ) The users of the database establish their view of the data and its structure without regards to the actual physical storage of the data. ii) That the database establishes a uniform high level of accuracy and consistency. Validation rules are applied by the DBMS. iii) The data should be available for use by application and by queries. iv) The data item prepared by one application are available to all applications or queries. No data items are owned by an application. v) The data base can be evolved according to application usage and query needs. Elements of DBMS: Elements of DBMS The elements of database management system are : (i) Database : Databases are banks and is an important constituent of any information system. Data bank for computerized information is organized in the form of a collection of file stored on secondary storage media. A file is a collection of records for each entity in the system. The record being a collection of data items representing the attributes of an entity. PowerPoint Presentation: ii) People : The people involved with the database system can be divided into2 groups: those who use the information system provided by the system and those who design develop and manage the system itself. iii) Database Planning and Design Technique : Since the database system involves people from all parts of organization with variety of information needs the development and operation of database system must be very carefully planned and managed. The data must be carefully designed to provide efficient excess to information required by different users PowerPoint Presentation: (iii) Computer Hardware and Software : Computer hardware and software for DBMS are two different important elements of DBMS. They are technological foundation of DBMS. What is Database Design? And objectives of Database Design? : What is Database Design? And objectives of Database Design? Database design is the process of designing the overall schema of database. This process is mainly divided in four phases: analysis phase, design phase refinement phase and physical design phase. PowerPoint Presentation: Analysis Phases : This is the initial phase of database design which includes the specification of data stored; operation applied on the stored data and description of application which use the data stored. This phase also takes care of existing system, its requirements and operation performed, so that expectation from the new system can be understood PowerPoint Presentation: Design Phase : It is not real analysis of enterprise. The output of the design phase is directly converted into real database. This is divided into two parts : a) Conceptual Design : The information gathered in first phase is converted into data model which is used to specify data stored, data relationship and constraints applied on stored data. b) Logical Design : Information represented in data model is converted into database schema of chosen DBMS or the conceptual schema mentioned above is applied for implementation from database schema. PowerPoint Presentation: Refinement Phase : This phase is used to correct problems which are encountered while analyzing the relations of database schema. This phase is used to i) Analyze the relations. ii) Identify the anomalies. iii) Refine database schema to correct or remove anomalies. PowerPoint Presentation: Physical design : This phase is used to create physical schema corresponding to the logical schema. It is used to specify internal storage structure and file organization that is required to store the data. Q.3 What is Database Management System? Discuss different models of Database. Which is mostly used and why? : Q.3 What is Database Management System? Discuss different models of Database. Which is mostly used and why? A data model is not just a way of structuring data: it also defines a set of operations that can be performed on the data. A data model is a mechanism that provides abstraction for the database application. Database modeling is used for representing entities of interest and their relationship in database. It allows the conceptualization of the association between various entities and their attributes. PowerPoint Presentation: Following are the different models of DBMS : • Hierarchical Model • Network Model • Relational Model Most database systems are built around one particular data model, although it is increasingly common for products to offer support for more than one model. Hierarchical Model :: Hierarchical Model : In a hierarchical model, data is organized into a tree-like structure, implying a single upward link in each record to describe the nesting, and a sort field to keep the records in a particular order in each same-level list. Hierarchical structures were widely used in the early mainframe database management systems, such as the Information Management System (IMS) byIBM. PowerPoint Presentation: This structure allows 1 : N relationship between two types of data. This structure is very efficient to describe many relationships in the real world;recipes, table of contents, ordering of paragraphs, any nested and sorted information. However, the hierarchical structure is inefficient for certain database operations when a full path is not included for each record. One limitation of the hierarchical model is its inability to efficiently represent redundancy in data. Network Model :: Network Model : The network model organizes data using two fundamental constructs, called records and sets. Records contain fields; Sets define one-to many relationships between records: one owner, many members. A record may be an owner in any number of sets, and a member in any number of sets. PowerPoint Presentation: The network model is a variation on the hierarchical model, to the extent that it is built on the concept of multiple branches emanating from one or more nodes. The model differs from the hierarchical model as in network model branches can be connected to multiple nodes. The network model is able to represent redundancy in data more efficiently than in the hierarchical model. PowerPoint Presentation: Although it is not an essential feature of the model, network databases generally implement the set relationships by means of pointers that directly address the location of a record on disk. This gives excellent retrieval performance, at the expense of operations such as database loading and reorganization. Relational Model :: Relational Model : Three key terms are used extensively in relational database models : relations, attributes, and domains. A relation is a table with columns and rows. The named columns of the relation are called attributes, and the domain is the set of values the attributes are allowed to take. PowerPoint Presentation: The basic data structure of the relational model is the table, where information about a particular entity is represented in columns and rows, also called tuples. Thus, the "relation" in "relational database" refers to the various tables in the database; a relation is a set of tuples. The columns enumerate the various attributes of the entity and a row is an actual instance of the entity that is represented by the relation. As a result, each tuple of the employee table represents various attributes of a single employee. PowerPoint Presentation: All relations in a relational database have to adhere to some basic rules to qualify as relations. First, the ordering of columns is immaterial in a table. Second, there can't be identical tuples or rows in a table. And third, each tuple will contain a single value for each of its attributes. PowerPoint Presentation: The flexibility of relational databases allows programmers to write queries that were not anticipated by the database designers. As a result, relational databases can be used by multiple applications in ways the original designers did not foresee, which is especially important for databases that might be used for a long time. This has made the idea and implementation of relational databases very popular with business organization.