DBMS

Classification of database management system is based on various parameters such as the kind of data model used to construct the DBMS, the number of users that will be using the database system, the way in which the database is distributed. In the section ahead, we will be discussing all the criteria on which the database system can be classified. Classification of Database … [Read more...] about Classification of Database Management System

Domain relational calculus (DRC) is a formal query language that is 'non-procedural' and 'declarative'. Being a form of relational calculus the domain relation calculus also specifies what information has to be retrieved, not how that information has to be retrieved.  Domain relational calculus is much similar to the tuple relational calculus the only difference is that the … [Read more...] about Domain Relational Calculus

Tuple relational calculus is a formal query language that we use to retrieve information from the relational database. It is a non-procedural query language, that only states what information has to be retrieved but, it does not state how the particular information has to be retrieved. We also refer to the tuple relational calculus as a declarative query language as it … [Read more...] about Tuple Relational Calculus

The database system environment is comprised of the components that are meant for defining and managing the data that we collect, store, manage and use in the database environment. In the section ahead, we will discuss all the components that constitute the database environment and along with this, we will also discuss the system utilities that are used to control and manage … [Read more...] about Database System Environment

Entity and attribute are the most common terms of DBMS. The fundamental difference between the entity and attribute is that an entity is an object that exists in a real-world and can be easily distinguished among all other objects of real-world whereas, the attributes define the characteristics or the properties of an entity on the basis of which it is easily distinguishable … [Read more...] about Difference Between Entity and Attribute in Database

Aggregate functions in SQL evaluate the set of values and return a single value as a result. SQL has five aggregate functions count, average, maximum, minimum, sum. The aggregate functions, 'sum' and 'average' operate only on numeric values. While count, maximum, minimum can also operate on non-numeric data such as string. In this section, we will discuss the steps to … [Read more...] about Aggregate Functions in SQL

Set operations integrate the outcome of two entirely independent SQL queries. There are three set operations in SQL Union, Intersect, Except. These set operations are based on the principles of mathematical set theory. The set operations are applicable to the type compatible relations only, that means relations involved in operation must have an 'equal number of attributes' and … [Read more...] about Set Operations in SQL

­Integrity constraints ensure that when the authorized users modify the database they do not disturb the data consistency. Integrity constraints are introduced while designing the database schema. The constraints are specified within the SQL DDL command like 'create table' and 'alter table' command. Let’s see, the general form of 'create table' and 'alter table' command … [Read more...] about Integrity Constraints in DBMS

Null Value in SQL is the special value, allocated to an attribute in a relation that indicates, the information regarding the corresponding attribute is either unknown or doesn’t even exist. In this section, we will discuss the null values in detail. What is the Null Value in SQL? The null value assigned to an attribute in a relation specifies that the value for the … [Read more...] about Null Value in SQL

SQL Data Definition Language defines the set of relations in a database. SQLs DDL specifies the schema of each relation in the database and also the relevance between the relations in a database. So in this section, we will discuss SQL data definition language in detail. Content: SQL Data Definition Language Data Definition Language in SQL SQL Data Types DDL … [Read more...] about SQL Data Definition Language (DDL)