Key is a data item which is used to identify a record or a value used to identify a record in a database is called a key. It helps uniquely to identify an entity from an entity set.Key allows us to identify a set of attributes that make them sufficient to distinguish entities from each other.ExampleAccount number, employee number, customer number are used as key fields because they specifically identify a record stored in a database.Different types of keysThe different types of keys in the database management system (DBMS) are as follows −Primary keySuper keyCandidate keyAlternate keyArtificial keyForeign keyPrimary, super, ... Read More

Key is a data item which is used to identify a record or a value used to identify a record in a database is called a key. It helps uniquely to identify an entity from an entity set.Key allows us to identify a set of attributes that make it sufficient to distinguish entities from each other.ExampleAccount number, employee number, customer number are used as key fields because they specifically identify a record stored in a database.Different types of keysThe different types of keys in the database management system (DBMS) are as follows −Primary keySuper keyCandidate keyAlternate keyArtificial keyForeign keyPrimary, super, ... Read More

The number of entity types which took part in the entity relationship is called the degree of relationships.There are three different types of degree of relationships, they are as follows −Unary relationshipBinary relationshipTernary relationshipUnary relationshipIt is the relationship between the instances of a single entity type. It is also called a recursive relationship.ExampleA person is married is a one-to-one relationship between the instances of Person entity type of unary relationship.Binary relationshipIt is the relationship between the instances of two different entity types. Two entities will participate in the relationship.For ExamplePerson and events are two different entity types which are related ... Read More

In the view of databases, cardinality refers to the uniqueness of data values that are contained in a column. High cardinality is nothing but the column contains a large percentage of totally unique values. Low cardinality is nothing but the column which has a lot of “repeats” in its data range.Cardinality between the tables can be of type one-to-one, many-to-one or many-to-many.Mapping CardinalityIt is expressed as the number of entities to which another entity can be associated via a relationship set.For binary relationship set there are entity set A and B then the mapping cardinality can be one of the ... Read More

Constraints are used for modeling limitations on the relations between entities.There are two types of constraints on the Entity Relationship (ER) model −Mapping cardinality or cardinality ratio.Participation constraints.Mapping CardinalityIt is expressed as the number of entities to which another entity can be associated via a relationship set.For the binary relationship set there are entity set A and B then the mapping cardinality can be one of the following −One-to-oneOne-to-manyMany-to-oneMany-to-manyOne-to-one relationshipAn entity set A is associated with at most one entity in B and an entity in B is associated with at most one entity in A.One-to-many relationshipAn entity set A ... Read More

A database model is a logical structure of a database, which contains the relationships and constraints that determine about how data is stored and accessed. The individual database models are designed based on the rules and concepts. Most data models can be represented by an accompanying database diagram.Types of database modelsThere are so many database models, but most used database models are −Hierarchical database modelRelational modelNetwork modelObject-oriented database modelThe major differences between the hierarchical, network and the relational models are as follows −Hierarchical ModelNetwork ModelRelational ModelOne to many or one to one relationship.Allowed the network mode to support many to ... Read More

The different user-friendly interfaces provided by the database management system (DBMS) are as follows −Menu-Based interfaces.Forms-based interfaces.Graphical user interfaces.Natural language interfaces.Speech input and output interfaces.Interfaces for parametric users.Interfaces for the database administrator (DBA).User friendly interfacesLet’s discuss the user-friendly interfaces provided by the DBMS in detail.Menu-based interfacesThese interfaces contain the lists of options through which the user is able to send the request.The Pull-down menus are a very popular technique in web-based user interfaces.These types of interfaces are mainly used by the web browsing users and web clients.Forms-based interfacesThese types of interfaces are displaying a form to each user. The user ... Read More

The database management system (DBMS) software is divided into several components. Each component will perform a specific operation. Some of the functions of the DBMS are supported by operating systems.The DBMS accepts the SQL commands that are generated from a variety of user interfaces, which produces a query evaluation plan, executes these plans against the database, and returns the answers.Let’s have a look on the major software components of DBMS with pictorial representation −ComponentsThe components of the DBMS are as follows −DBA − The Data Base Administrator (DBA) responsibility is to create the DBMS structure and have the ability to ... Read More

Entity relationship diagram is the graphical representation of entities and relationships among those entities in the database.ExampleConversion of ER diagrams to tablesFollow the steps given below for the conversion of the ER diagrams to tables in the database management system (DBMS) −Step 1 − Conversion of strong entitiesFor each strong entity create a separate table with the same name.Includes all attributes, if there is any composite attribute divided into simple attributes and has to be included.Ignore multivalued attributes at this stage.Select the p key for the table.Step 2 − Conversion of weak entityFor each weak entity create a separate table ... Read More

ER model stands for the Entity Relationship Model in the database management system (DBMS). It is the first step of designing to give the flow for a concept. It is the DFD (Data Flow Diagram) requirement of a company.It is the basic building block for relational models. Not that much training is required to design the database project. It is very easy to convert the E-R model into a relational table or to a normalized table.It is a high-level data model diagram that defines the conceptual view of the database. It acts as a blueprint to implement a database in ... Read More