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
The company is organized into departments. Each department has a unique name, a unique number, and a particular employee who manages the department. We keep track of the start date when that employee began managing the department. A department may have several locations. A department controls a nu...
Data is converted into information, and information is then evaluated and organised so that it can be used purposefully as knowledge.
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 maintai...
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 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 specialization relationship may also be referred to as a superclass-subclass relationship. Higher- and lower-level entity sets also may be designated by the terms superclass and subclass, respectively. The person entity set is the superclass of the employee and student subclasses.
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.
A primary goal of a database system is to retrieve information from and store new information into the database. People who work with a database can be categorized as database users or database administrators.
The basic structure of an SQL query consists of three clauses: select, from, and where.
Databases are widely used in enterprises, banking and finance, universities, airlines, telecommunication, etc.
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 architecture of a database system is greatly influenced by the underlying computer system on which the database system runs. Database systems can be centralized, or client-server, where one server machine executes work on behalf of multiple client machines.
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
A query language is a language in which a user requests information from the database.
we discuss differences between specialization/generalization lattices (multiple inheritance) and hierarchies (single inheritance), and elaborate on the differences between the specialization and generalization processes during conceptual database schema design. We discuss constraints that apply ...
In this section we discuss the concepts of concurrent execution of transactions and recovery from transaction failures
All procedural relational query languages provide a set of operations that can be applied to either a single relation or a pair of relations.
XML (Extensible Markup Language)—has emerged as the standard for structuring and exchanging data over the Web. XML can be used to provide information about the structure and meaning of the data in the Web pages rather than just specifying how the Web pages are formatted for display on the screen
Conceptual modeling is a very important phase in designing a successful database application. Generally, the term database application refers to a particular database and the associated programs that implement the database queries and updates.
Four main control measures are used to provide security of data in databases: Access control, Inference control, Flow control, Data encryption
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.
A database system provides a data-definition language to specify the database schema and a data-manipulation language to express database queries and updates.
A relational database is based on the relational model and uses a collection of tables to represent both data and the relationships among those data.
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.
The main idea of Sampling Algorithm is to select a small sample , one that fits in main memory , of the database of transaction
Researchers have developed several data-models to deal with these application domains, including object-based data models and semi-structured data models.
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 relational database consists of a collection of tables, each of which is assigned a unique name.
A database schema, along with primary key and foreign key dependencies, can be depicted by schema diagrams.