Download CBSE Class 11 Informatics Practices Relational Database Management System Notes And Questions in PDF format. All Revision notes for Class 11 Informatics Practices have been designed as per the latest syllabus and updated chapters given in your textbook for Informatics Practices in Standard 11. Our teachers have designed these concept notes for the benefit of Grade 11 students. You should use these chapter wise notes for revision on daily basis. These study notes can also be used for learning each chapter and its important and difficult topics or revision just before your exams to help you get better scores in upcoming examinations, You can also use Printable notes for Class 11 Informatics Practices for faster revision of difficult topics and get higher rank. After reading these notes also refer to MCQ questions for Class 11 Informatics Practices given our website
Relational Database Management System And Questions Class 11 Informatics Practices Revision Notes
Class 11 Informatics Practices students should refer to the following concepts and notes for Relational Database Management System And Questions in standard 11. These exam notes for Grade 11 Informatics Practices will be very useful for upcoming class tests and examinations and help you to score good marks
Relational Database Management System And Questions Notes Class 11 Informatics Practices
RELATIONAL DATABASE MANAGEMENT SYSTEM
Basic/raw facts about something which is not organized, for example details of some students which is not organized.
Each piece of information about an entity, such as name of a person or address, age or name of a product or the price is a Data Item.
A well organised collection of data that ensures safety, security and integrity of data.
DataBase Management System(DBMS)
Comprehensive software that provides the essential services to create, manage and maintain the databases. In short a DBMS provides the means to store the data in the database, to edit or delete the data stored, to search and analyze the data in the database. They also provide various safety and security mechanisms that ensures that in any case stored data will be safe and accessible.
Relational DataBase Management System(RDBMS) :
A Database Management System that conforms at-least half of the 12 rules defined by Dr. E.F. Codd (1970) in his research document. In a relational data model, the data is organized into tables (i.e. Rows and Columns). These tables are called Relations. A row in a table represents a relationship among a set of values. Since table is a collection of relationships it is generally referred to using the mathematical term Relation.
Systems comprising of Databases and Database Management Systems are simply referred as database systems.
Advantages of Data Base System:
1) Reduce data redundancy (duplication of data)
2) Control data inconsistency to a large extent
3) Database facilitate sharing of data
4) Enforce standards
5) Centralized databases can ensure data security
Examples of Common Database Management Systems:
MySQL ,INGRES, POSTGRES, ORACLE, DB2.
Levels of Database Implementation:
1. Internal Level ( Physical Level) :
It describes how the data are actually stored on the storage media.
2. Conceptual Level :
It describes what data are actually stored in the database. It also describes the relationships existing among data.
3. External Level (View Level) :
It is closest to the users and is concerned with the way in which the data are viewed by individual users External Level
Data Independence: The ability to modify a scheme definition in one level without affecting a scheme definition in the next higher level.
Two Level of Data Independence:
1. Physical Data Independence: It refers to the ability to modify the scheme followed at the physical level without affecting the scheme followed at the conceptual level.
2. Logical data Independence It refers to the ability to modify the scheme followed at the conceptual level without affecting the scheme followed at the External level.
A way by which data structures and their relationships are analyzed.
Different Data Models :
1. Relational data model
2. Network data model
3. Hierarchical data model
Relational data model:
In this model data is organized into tabular structures called relations. A database may contain many relations providing a better classification of data based on its nature and use. Multiple relations are then linked/ associated together on some common key data values (foreign key).
Network Data Model :
In this model data is represented by collections of records and relationships among data are represented by links. A record is collection of fields i.e. attributes, each of which contents only one data value.
Hierarchical data model :
In this model records are organized as trees, data is represented by collection of records connected to one another through links.
Basics of Relational Model
A tabular structure containing data. To be a relation is must satisfy following four conditions:
• Atomicity : At every row-column intersection (Cell) there must be an atomic value i.e. a value that can not be further subdivided.
• No duplicity: No two rows of relation will be identical i.e. in any two rows value in at least one column must be different.
• Ordering of rows is immaterial.
• Ordering of columns is immaterial.
A row in a relation is called a tuple
A column in a relation is called an attribute
Domain of an attribute refers to the set of all the possible values for that attribute.
Number of attributes in a relation is the degree of that relation
Number of tuples in a relation is the cardinality of that relation.
A set of one or more minimal attributes used to uniquely identify a tuple in the relation
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