CLASS 12TH DATABASE -MY SQL

 

MYSQL

 It is freely available open source Relational Database Management System (RDBMS) that uses Structured Query Language(SQL). In MySQL database , information is stored in Tables. A single MySQL database can contain many tables at once and store thousands of individual records.

SQL (Structured Query Language)

SQL is a language that enables you to create and operate on relational databases, which are sets of related information stored in tables

DIFFERENT DATA MODELS

 A data model refers to a set of concepts to describe the structure of a database, and certain constraints (restrictions) that the database should obey. The four data model that are used for database management are :

 1.Relational data model : In this data model, the data is organized into tables (i.e. rows and columns). These tables are called relations.

 2. Hierarchical data model

 3. Network data model

 4. Object Oriented data model

RELATIONAL MODEL TERMINOLOGY

1. Relation : A table storing logically related data is called a Relation.

2. Tuple : A row of a relation is generally referred to as a tuple.

 3. Attribute : A column of a relation is generally referred to as an attribute.

 4. Degree : This refers to the number of attributes in a relation.

5. Cardinality : This refers to the number of tuples in a relation

. 6. Primary Key : This refers to a set of one or more attributes that can uniquely identify tuples within the relation.

7.Candidate Key : All attribute combinations inside a relation that can serve as primary key are candidate keys as these are candidates for primary key position.

8. Alternate Key : A candidate key that is not primary key, is called an alternate key.

9. Foreign Key : A non-key attribute, whose values are derived from the primary key of some other table, is known as foreign key in its current table.