Select Statement-:A select statement retrieves information from the database. Using a SELECT statement, We can do the following: Select : We can use the selection capability in SQL to choose the rows in a table that we want returned by a query. We can use various criteria to selectively restrict the rows that we see.… Read More »
introduction- SQL means structure query language.To access the database, we execute a Structured Query Language (SQL) statement, which is the American National Standards Institute (ANSI) standard language for operating upon relational database. The language contains a large set of operators for partitioning and combining relations. the database can be modified using the SQL statements. Non-Procedural… Read More »
Introduction -: Now a days relation data model is being used as the primary model for commercial data processing application. It was introduced by E.F.Codd in 1970 and it changed permanently the way people viewed database. The relation model is based on logical relationship between data and allows user to be totally unconcerned with or… Read More »
Convert ER model into relation schema . There are well defined rules for this conversion. These are Converting strong Entity type Converting weak entity types Converting relationships Converting specialization Converting aggregation. Converting strong entity types- Each entity become a table Each single valued attribute becomes a column Derived attribute are ignored. Composite attribute are represented… Read More »
The Entity Relationship Model has describe some following steps are available here. There are Identify the entity Identify the attribute Find the relationship Identify other relevant attribute Draw complete E-R Diagram with all attribute including primary key For understating these steps complete we take a example of a college database .. A collage… Read More »
There are many important features are available in extended features of E R model.These are .. Superclass and Subclass Specialization Generalization Condition defined v/s User defined Disjoint vs Overlapping Total vs Partial specialization … Read More »
E-R-Model describe data and identifies relationship between them.E-R model is represented by E-R Diagram.E-R- model is explained along with their represented in E-R Diagram. Attribute : Properties or characteristic y possessed by an entity are called attributes. Relationship-: A Relationship is an association between entities. A relationship is represented as a diamond between two… Read More »
An entity relationship diagram is a graphical representation of an organization data storage requirements. Entity relationship diagram are abstraction of the real word which simplify the problem to be solved while retaining its essential feathers. E-R-model diagrams are used to .. Identify the data that must be captured stored and retrieved in order to support… Read More »
Data models-: These models are- a collection of conceptual tools for describing data, data relationship,data semantics and data constraints. in other words we can say that the Data models define how data is connected to each other and how they are processed and stored inside the system. Data Models are categorized into the following – 1.… Read More »
A database structure is divided in different components. The exact structure of a DBMS is depended upon the operating system on which it has to work because the operating system provide the basic services, which database system uses base for accomplishing it’s tasks. Database structure—- A database system are divided in two types… Query… Read More »