Data base management system (DBMS) represent the management of data which includes various processes like collection of related data , storing and retrieving them, using set of programs for easy and effective manner. While it may sound quit simple and easy but in reality it is not. As the bulk of data increases with the complexity of systems and multiple process running head to head it leads to most feared complication called Deadlock. It is nightmare for the developers and programmers. We will be discussing in detail everything about this evil Deadlock in our following article below. Starting with the definition first. [Read more…] about What is Deadlock ? – Definition
The database is a repository of all types of data. After storing it, there should be a mechanism to access, manipulate and update it. For this, we have a tool in the form of a query to perform all these operations. There are many query language like SQL, Search Engine Query Language (Google, Bing), DMX (Data Mining Language), etc. All these languages have different function and their function structure used for the different data model. [Read more…] about What is database query? Definintion
The database schema is a structure or architecture to store data in the database. It creates abstraction(hide the lowest level the detail from the user) between application and physical database. A user creates a relationship with the help of Database Management System.But a user can’t see which type of data structure is used by the system to store the data in it.This data structure may be linear and may be non-linear, we don’t know. This is known as Abstraction. The database divided into three-level architecture is also known as three; schema architecture. [Read more…] about database schema | what is schema architecture
Relation Algebra is a procedural query language for RDBMS (Relational Database Management System). An Algebra based on the set of operators (like Arithmetic operator, union, intersection relational operator, etc.) and operand. Edgar F. Codd created it for a relational database. Relational Algebra provides a fundamental query for retrieving data from databases. The retrieved result from algebra expression is a relation which formed from one or more relations. Relational Algebra specifies many operations to manipulate relations. [Read more…] about Relational Algebra – What is Relational Algebra?
The database is the location to store the data. Firstly we used excel sheet to store the data. However, it has some problem with data integrity and redundancy problem. This problem solved by E.F. Codd proposed a model in 1970. This model was straightforward. It used the concept of mathematical relation which looks like a table. [Read more…] about What is relational database? – Definition
Data recovery is the art of restoring lost or damaged files. This damage can occur when your computer crashes, a virus infects, you accidentally reformat a disk that contains precious data, or you experience some other catastrophe of considerable dimension. And, at some point in your life, you’re going to delete a file you really didn’t mean to (believe me). The next time tragedy strikes, try running one of the many data recovery applications (powerful software written specifically for data recovery purposes) to see if it can correct the situation. Often these little jewels work magic and save your day-and your files. [Read more…] about What is Data Recovery?
In a computer database, the database engine is the software that does the real work of sorting the information, finding specific data that you request, and so on. The term used to refer to a separate piece of software that ran on a central computer (in this case, it is more or less synonymous with the term “back-end”). Widely used database engines include Oracle, DB2, and Sybase. Separate front-end software running on your own computer lets you tell the database engine what to do (how to sort the data, what data to find), and displays the results of your commands. [Read more…] about What is Database Engine?
A database document is just a collection of information stored in computerized form. The simplest way to understand a database is to think of it like a set of 3 x 5 cards. Since the information is on your computer, though, a dick of the mouse or the stroke of a key can alphabetize those “cards,” or find just the names of the people on the cards who live in a certain town, or tell you who owes how much money, and so on. [Read more…] about What is Database?
Attributes means characteristics. For instance, in a database or a spreadsheet you can apply attributes to each field or cell to customize your document. As a general attribute, you can choose whether it is to be a text field or a numeric field or perhaps a computed field, whose value the application calculates for you.
Then you can apply more specific attributes to the field or cell, such as making the text bold and right-aligned and perhaps in a particular typeface. If a field is numeric, you will have other attribute options available, such as how many decimal places to display, whether to use a dollar sign or a percent symbol, or whether to start a formula in the cell.
Relation schema: A set of attributes is called a relation schema (or relation scheme). A relation schema is also known as table schema (or table scheme). A relation schema can be thought of as the basic information describing a table or relation. It is the logical definition of a table. Relation schema defines what the name of the table is. This includes a set of column names, the data types associated with each column. [Read more…] about What is Difference Between Relation and Relational Schema?
A functional dependency is an association between two attributes of the same relational database table. One of the attributes is called the determinant and the other attribute is called the determined. For each value of the determinant there is associated one and only one value of the determined. [Read more…] about Type of Functional Dependence (FD)
The E-R model can result problems due to limitations in the way the entities are related in the relational databases. These problems are called connection traps. These problems often occur due to a misinterpretation of the meaning of certain relationships. [Read more…] about What are the Problems with E-R Model?
The entity set which does not have sufficient attributes to form a primary key is called as Weak entity set. An entity set that has a primary key is called as Strong entity set. Consider an entity set Payment which has three attributes: payment_number, payment_date and payment_amount. Although each payment entity is distinct but payment for different loans may share the same payment number. Thus, this entity set does not have a primary key and it is an entity set. Each weak set must be a part of one-to-many relationship set. [Read more…] about What are Strong and Weak Entity Sets in DBMS
There is no standard for representing data objects in ER diagrams. Each modeling methodology uses its own notation. [Read more…] about E-R NOTATION
In Entity-Relationship model a database is modeled as a collection of entities and relationship among entities. The ER model views the real world as a construct of entities and association between entities. [Read more…] about What is the Basic Construction of E-R Modeling?
There are two techniques used for the purpose of data base designing from the system requirements. These are:
• Top down Approach known as Entity-Relationship Modeling
• Bottom Up approach known as Normalization. [Read more…] about What is ER-Model?Advantages and Disadvantages of E-R Model.
Relational model stores data in the form of tables. This concept purposed by Dr. E.F. Codd, a researcher of IBM in the year 1960s. The relational model consists of three major components: [Read more…] about Relational Model
The Network model replaces the hierarchical tree with a graph thus allowing more general connections among the nodes. The main difference of the network model from the hierarchical model, is its ability to handle many to many (N:N) relations. In other words, it allows a record to have more than one parent. Suppose an employee works for two departments. The strict hierarchical arrangement is not possible here and the tree becomes a more generalized graph – a network. The network model was evolved to specifically handle non-hierarchical relationships. As shown below data can belong to more than one parent. Note that there are lateral connections as well as top-down connections. A network structure thus allows 1:1 (one: one), l: M (one: many), M: M (many: many) relationships among entities. [Read more…] about Network Model
A model is a representation of reality, ‘real world’ objects and events, associations. It is an abstraction that concentrates on the essential, inherent aspects an organization and ignores the accidental properties. A data model represents the organization itself. It should provide the basic concepts and notations that will allow database designers and end users unambiguously and accurately to communicate their understanding of the organizational data. [Read more…] about What are Data Models? Type of Data Models.
A DBMS performs several important functions that guarantee integrity and consistency of data in the database. Most of these functions are transparent to end-users. There are the following important functions and services provided by a DBMS: [Read more…] about What are the Functions and Service of DBMS
A typical structure of a DBMS with its components and relationships between them is show. The DBMS software is partitioned into several modules. Each module or component is assigned a specific operation to perform. Some of the functions of the DBMS are supported by operating systems (OS) to provide basic services and DBMS is built on top of it. The physical data and system catalog are stored on a physical disk. Access to the disk is controlled primarily by as, which schedules disk input/output. Therefore, while designing a DBMS its interface with the as must be taken into account. [Read more…] about What are the Components of DBMS?
A DBMS must provide appropriate languages and interfaces for each category of users to express database queries and updates. Database Languages are used to create and maintain database on computer. There are large numbers of database languages like Oracle, MySQL, MS Access, dBase, FoxPro etc. SQL statements commonly used in Oracle and MS Access can be categorized as data definition language (DDL), data control language (DCL) and data manipulation language (DML). [Read more…] about Database Languages
A metadata (also called the data dictionary) is the data about the data. It is the self describing nature of the database that provides program-data independence. It is also called as the System Catalog. It holds the following information about each data element in the databases. [Read more…] about What is Metadata OR Data Dictionary?
Functions of Data Base Administrator
Data Base Administrator (DBA) is a person or group in charge for implementing DBMS in an organization. Database Administrator’s job requires a high degree of technical expertise and the ability to understand and interpret management requirements at a senior level. In practice the DBA may consist of team of people rather than just one person. [Read more…] about What is the role of DBA, Data Manager, File Manager, and Disk Manager?
Any access to the stored data is done by the data manager. A user’s request for data is-received by the data manager, which detern1ines the physical record required. The decision as 10 which physical record is needed may require some preliminary consultation of the database and/or the data dictionary prior to the access of the actual data itself. [Read more…] about What is the Procedure for Database Access?
A major objective for three-level architecture is to provide data independence, which means that upper levels are unaffected by changes in lower levels. [Read more…] about What is Data Independence of DBMS?
Database changes over time when information is inserted or deleted. The collection of information stored in the database at a particular moment is called an instance of the database. The overall design of the database is called the database schema. [Read more…] about What are INTANCES, SCHEMAS AND SUBSCHEMA in DBMS?
DBMS A database management system is the software system that allows users to define, create and maintain a database and provides controlled access to the data. [Read more…] about What is DBMS? Advantages and Disadvantages of DBMS.