A database system is partitioned into modules that deal with each of the responsibilities of the overall system. The functional components of a database system can be broadly divided into the storage manager and the query processor components.
Self-describing nature of a database system Insulation between programs and data, and data abstraction Support of multiple views of the data Sharing of data and multiuser transaction processing
A database system is a collection of interrelated data and a set of programs that allow users to access and modify these data. A major purpose of a database system is to provide users with an abstract view of the data. That is, the system hides certain details of how the data are stored and maint...
A transaction is a collection of operations that performs a single logical function in a database application.
The similarities and differences between conceptual modeling and knowledge representation, and introduces some of the alternative terminology and a few additional concepts.The goal of KR techniques is to develop concepts for accurately modeling some domain of knowledge by creating an ontology that d...
There are several implicit relationships among the various entity types. In fact, whenever an attribute of one entity type refers to another entity type, some relationship exists. For example, the attribute Manager of DEPARTMENT refers to an employee who manages the department; the attribute
This chapter discusses techniques for securing databases against a variety of threats. It also presents schemes of providing access privileges to authorized users.
Information processing drives the growth of computers, as it has from the earliest days of commercial computers. In fact, automation of data processing tasks predates computers.
The individual entity instances in an entity set and the individual relationship instances in a relationship set. In ER diagrams the emphasis is on representing the schemas rather than the instances.
The database schema is the logical design of the database.
Sensitivity of data is a measure of the importance assigned to the data by its owner, for the purpose of denoting its need for protection. Some databases contain only sensitive data while other databases may contain no sensitive data at all.
The basic structure of an SQL query consists of three clauses: select, from, and where.
An entity type DEPARTMENT with attributes Name, Number, Locations, Manager, and Manager_start_date. Locations is the only multivalued attribute. We can specify that both Name and Number are (separate) key attributes because each was specified to be unique
A database schema, along with primary key and foreign key dependencies, can be depicted by schema diagrams.
Data is converted into information, and information is then evaluated and organised so that it can be used purposefully as knowledge.
Database design mainly involves the design of the database schema. The design of a complete database application environment that meets the needs of the enterprise being modelled requires attention to a broader set of issues.
Several types of locks are used in concurrency control. To introduce locking concepts gradually, first we discuss binary locks, which are simple, but are also too restrictive for database concurrency control purposes, and so are not used in practice. Then shared/exclusive locks - also known as read/...
Specialization is the process of defining a set of subclasses of an entity type; this entity type is called the superclass of the specialization. We use the term generalization to refer to the process of defining a generalized entity type from the given entity types.
The UML methodology is being used extensively in software design and has many types of diagrams for various software design purposes. We only briefly present the basics of UML class diagrams here, and compare them with ER diagrams
A database usually contains groups of entities that are similar. For example, a company employing hundreds of employees may want to store similar information concerning each of the employees. These employee entities share the same attributes, but each entity has its own value(s) for each attribut
The database administrator (DBA) is the central authority for managing a database system. The DBA’s responsibilities include granting privileges to users who need to use the system and classifying users and data in accordance with the policy of the organization
IBM developed the original version of SQL, originally called Sequel, as part of the System R project in the early 1970s.
A query language is a language in which a user requests information from the database.
SQL permits a variety of functions on character strings. Read to know about them.
A database-management system (DBMS) is a collection of interrelated data and a set of programs to access those data.
it is sometimes necessary to represent a single superclass/subclass relationship with more than one superclass, where the superclasses represent different entity types. In this case, the subclass will represent a collection of objects that is a subset of the UNION of distinct entity types.
DBMS typically includes a database security and authorization subsystem that is responsible for ensuring the security of portions of a database against unauthorized access
Entities and Their Attributes. The basic object that the ER model represents is an entity, which is a thing in the real world with an independent existence. An entity may be an object with a physical existence (for example, a particular person, car, house, or employee)