SQL Joins SQL Joins: A joins is a relational operation that combines row in one table to the rows in another table related table according to common values existing in corresponding columns such as primary and foreign key columns. The joins condition is specified with WHERE clause of SELECT statement. You may join two tables if each one contains a column with same domain of values. It must be noted that to join multiple tables, there should be one WHERE condition for each pair of tables being joined. Thus if N tables are to be combined, there should be N-1…
Author: Kritika mishra
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Structure Query Language Structure Query Language (SQL) is the most popular and widely used relational standard database language. It is easy to learn and use. It allows the user to define, retrieve and to manipulate the data in the table of database. It was designed and implemented at IBM Research as an interface in an experimental relational database system called System R. This language became the basis for IBM’s first commercially available relation database system. This language is accepted as a standard database language by ANSI and ISO. SQL History The development of SQL began at IBM in the mid-1970s…
Using quantum key distribution for cryptographic purposes: A survey with real implementation problems Abstract Information security/information hiding has become the main concern of the current era, and the technique of cryptography is widely used for this purpose. Using various secret key agreement techniques, a secret cryptographic key is shared between the concerned parties for encryption and decryption of the data in cryptography. In this article, the characteristics of the various current key establishment methods are reviewed and compared. According to the Cryptography, a key establishment primitive, QKD (Quantum Key Distribution) does not provide a stand-alone security service on its own. Therefore,…
Normalization In Database Normalization In Database: The process to convert the complex data structure into simple and stable data structure is called normalization. The purpose of normalization is to produce a stable set of relations. Basically, a normalized relation has a simple structure, than an un-normalized one. By applying the normalization principles, we can improve the stability of the relations. Normalization Steps Normalization is often accomplished in steps, each of which corresponds to a normal form. A normal form is a state of a relation that can be determined by applying simple rules regarding dependencies to that relation. A brief…
Data Integrity Data Integrity: Data integrity refers to the correctness and consistency of data. It is another form of database protection or security, security involves protecting the data from unauthorized operations, while integrity is concerned with the quality of data itself. The data integrity plays an important role in RDBMS, in which multiple users access the data from database. Integrity is usually expressed in terms of the certain constraints. These are the consistency rules that can be applied to database so that the correct data can be entered into the database. The constraints may be applied to individual data items…
Cardinality In E-R Diagram Cardinality In ER Diagram: In a relational database model, the number of records in a table or relation is called cardinality in the E-R Model of the database. However, relationship types usually have certain constraints that limit the number of instance of one entity type that can be associated with each instance of another related entity type. Therefore, the cardinality of a relationship is defined as; the number of instances of one entity type that can be associated with each instance of another related entity type. Suppose there are two entity types A and B that…
Relationship in Database Relationship In Database: A relationship is an association between the instances of one or more entity types in the database which represents some information. For example, a student may be related to a class by being enrolled in that class in different universities, college and school. Another example is the link between mother and children. One mother may have many children, but each children has only one mother. A relationship between entities is given a relevant name that represent some data in the data file. or example there is a relationship between Manager and Department in the…
Elements Of ER Model Elements Of ER Model: We know that E-R model describes the data as entities, attributes and relationship between entities. So the major elements of E-R model are entities, associated attributes of entities and relationship. The elements of E-R model are Entities Attributes Relationship Entity The basic object that the E-R Model represents is an entity, which is “a thing’’ in real world with an independent existence which is the most important item in the data file of E-R Model. You can also say that anything in a real world that has a set of different attributes…
Entity Relationship Model Entity Relationship Model: The Entity-Relationship Model (or E-R Model) is a popular high conceptual data model. Peter Chen introduced this model in 1976 and is widely used for local design. The E-R model is used to construct the conceptual data model, which is the representation of the structure of the database that is independent of the DBMS software. The entity relationship model is mostly commonly used during the analysis phase of the database. The entity relationship model is expressed in terms of entities, relationships between the entities and the attribute or the properties of the involved entities.…
Database Administrator Database Administrator: The database administrator (DBA) plays an important role in DBMS environment. In a database management system, the primary resource is the database itself and the secondary resource is the DBMS and related software. Administering these resources and overall security of the database system is the responsibility of the DBA. The DBA is also responsible for designing, coordinating and monitoring the database system. The DBA is an IT professional. He must be technically competent, having excellent communication and management skills. The management skills such as (plan and coordinate) have importance for the database development phases, and to…
Phases In Database Development Process Phases In Database Development Process: The database development process comprises a series of phases where each of them has its own expertise. The major phases are planning, requirement analysis, and implementation. Each process is divided into steps. The diagram of these phases are shown as Planning The planning phase begins when a customer requests to develop a database project. It is a set of tasks or activities, which decide to the resource required in the database development and the time limit of different activities. During the planning phase, four major activities are performed these…
Database Development Process Database Development Process: The database is the fundamental component of the information system of an organization and any organization is blind without the data. In computerized environment, the information system includes the resources such as database, DBMS software, the application programs etc. The database development process is very important and creative task. The database development process consist of two activities. The first activity involves the design of the data content and the structure of the database. The second activity is related to the design of the database applications. The two activities are closely related to each other.…
Data Model In Database Data Model in Database: A representation of a real universal process, device or concept is known as Data Model. A data model (or database model) is a collection of concepts that can be used to describe the structure of the database. It means that the data types, relationship between data and constraints that should hold on the data are described. Most of the data model also includes a set of basic operations for specifying retrievals and updates procedure on the database. The purpose of the data model is to represent data and to make the data…
Database Language Database language is an important part of DBMS. It is used to access the required data from a database, to modify the data of database and to design the structure of database. A user uses a database language for interfacing with the DBMS to access the data from database. A user can either be an application programmer or an end-user. Mostly the application programmer insert the statements of the database access language into its program written in general purpose programming language (such as COBOL or C++ or Visual Basic or any fourth generation language). It is because database…
What is Data Dictionary in DBMS What is Data dictionary in DBMS: The data dictionary is also referred as data repository or system catalog. It is an important part of DBMS. It contains data about data. It means that the data dictionary contains the actual database description managed by DBMS. Data dictionary is automatically updated as data is inserted and updated with the passage of time. The data dictionary contains the following information Logical structure of database such as table name, column name of each table and their data types and other properties, indices created in a table, and stored…
What is Data Independence in Database What is Data Independence in Database: The separation of data from the application programs or user interfaces that uses the data is known as Data Independence.Data independence also means that data can be updated/added in master tables without adding data into child tables. Data independence is one of the important feature of DBMS. The three level architecture provide the concept of data independence in the data file of same organization, which means that the upper-levels are unaffected by changes to lower-levels of same file. The three level architecture makes it easier to achieve true…
Mapping In Database Mapping In Database. The process to convert a request and the result from one level to another level is known as Mapping. The mapping defines the correspondence between three levels. The mapping description is also stored in data dictionary in the same file of data. The DBMS is responsible for mapping between these three types of schemas in the database of the same file to represent it. There are two types of mapping External-Conceptual Mapping Conceptual-Internal Mapping External-Conceptual Mapping: An external-conceptual mapping defines the correspondence between a particular external view and conceptual view for representing…
Three Schema Architecture Three Schema Architecture: An early proposal states for a standardized terminology and architecture for database system were developed and published in 1971 by DBTG (Data Base Task Group) appointed by CODASYL. A similar architecture and terminology were developed and published in 1975 by SPARC (Standards Planning and Requirement Committee) of American National Institute (ANSI) for the data representation. As a result of these and later reports, database can be viewed at three levels, known as external, conceptual and internal levels. These levels form three level architecture . These levels are represented by three schemas or three models…
Relationship between DBMS and Application Program Relationship between DBMS and Application Program are very important.There is a very close relationship between DBMS and application programs. The application program provides the user-interface to send request to DBMS and to receive processed results from DBMS. The DBMS processes the request and returns the result to the application program and also controls and manages the database. In most of the database environment, application programs are created for interfacing with database. The user communicates with the database system through user interface part of the application program. The application program is developed according to requirement…
Advantages Of Database Management System Advantages of Database Management System are as follows: Controlling Data Redundancy Data Consistency Data Sharing Data Integration Integrity Constraints Data security Data Atomicity Database Access Language Development of Application Creating Forms Report Writes Control Over Concurrency Backup and Recovery Procedure Data Independency Advanced Capability Controlling Data Redundancy In non-database system each application program has its own files. In this case, the duplicated copies of the same data are created at many places in the same file. In DBMS the data redundancy can be controlled or reduced but is no removed completely. Sometime, it is necessary…