Relational Model | Relational calculas

RELATIONAL CALCULUS Relational algebra is concerned with a procedural language in which the user has to write the steps or procedure to obtain the required result.In this the user is not concerned with the detail of how to obtain information.          In relational calculus the user tell his requirement and the output is available without knowing the method about its...

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Relational Model | Integrity constraints over relation

INTEGRITY CONSTRAINTS OVER RELATION INTRODUCTION Database integrity refers to the validity and consistency of stored data. Integrity is usually expressed in terms of constraints, which are consistency rules that the database is not permitted to violate. Constraints may apply to each attribute or they may apply to relationships between tables. Integrity constraints ensure that changes (update...

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Relational Model | ER to Relational model conversion

ER TO RELATIONAL MODEL CONVERSION INTRODUCTION- In the E-R model, data is represented using entities, and relationships are defined between these entities. However, with the relational model, the entities and their relationships follow strict guidelines. Usually, an E-R model is first developed, and then it is transformed into a relational model. RULES TO CONVERT  ER TO RELATIONAL MODEL...

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Relational Model | Key constraints | Types of key

KEY CONSTRAINTS INTRODUCTION-A Key Constraint is a statement that a certain minimal subset of the fields of a relation is a unique identifier for a tuple. TYPES OF KEY CONSTRAINTS- Various types of key constraints are- Candidate key Super key Primary key Foreign key 1....

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Relational Query Languages| Basic sql query language

BASIC SQL QUERY LANGUAGE INTRODUCTION- SQL (Structured Query Language) is a special-purpose programming language designed for managing data held in a relational database management system (RDBMS). SQL became a standard of the American National Standards Institute (ANSI) in 1986, and of the International Organization for Standards (ISO) in 1987.  WHAT CAN SQL DO? • SQL can execute queries...

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Relational Query Languages | How to create table in sql

CREATING TABLES AND VIEWS CREATING TABLES CREATE: This command is used when we want to create a new table. syntax: create table <tname>  (col.1 data type (size) constraint <constraint name> not null , col.2 data type (size)); E.g.: create table mydoc1 (username varchar (20) constraint...

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Relational Query Languages |Data Manipulation Language(DML)

DML (Data Manipulation Language) The Data Manipulation Language (DML) is the subset of SQL used to add, update and delete data and select or retrieval. COMMAND USED-INSERT, UPDATE, DELETE,SELECT INSERT adds rows (formally tuples) to an existing table. UPDATE modifies a set of existing table...

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Relational Query Languages | Data Definition language(DDL)

DDL(Data Definition Language) The Data Definition Language (DDL) manages table and index structure. COMMAND USED- CREATE, ALTER, DROP,RENAME CREATE creates an object (a table) in the database. ALTER modifies the structure of an existing object in various ways, for    example, adding a column...

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Relational Query Languages | Data control language (DCL)

DCL(Data Control Language) The Data Control Language (DCL) authorizes users to access and manipulate data.         COMMAND USED- GRANT, REVOKE, COMMENT GRANT authorizes one or more users to perform an operation or a set of operations on an object. REVOKE eliminates a grant, which may be the default grant. COMMENT Adding the element into data dictionary 1.GRANT...

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