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IBPS PO Notes for Database Managements

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IBPS PO Notes for Database Managements

DATABASE MANAGEMENT

Database is collection of interrelated data and set of program to access this data in a convenient and efficient way.

A DBMS stores data in such a way that it becomes easier to retrieve, manipulate, and give information.

Architecture

DBMS is divided into three levels:

External view or user view or view level

It is highest level of data abstraction includes only those portion of database of concern to a user.

Conceptual view/logical level

Includes all the entities and relationship among them. It describes the schemas of database. DBA work at this level.

Internal view or physical level

This is the lowest level of DBMS. it describes how to store data data and access these data.

Keys

Key is defined a the combination of attributes that is used to identify record of the database table. It is also used to arrange the records.

  • Super key − A set of attributes that collectively identifies an entity in an entity set.
  • Candidate Key − Minimal super key is called a candidate key. An entity set may have more than one candidate
  • Primary Key − uniquely identify the entity set called primary
  • Foreign key– whose value is derived from the primary key of another table. Relationship held between two tables with the help of foreign

What is SQL

Structured query language

SQL is the language used to query all databases. It is simple learn and appears to do very little but is the heart of a successful database application.

DML  :  DATA MANIPULATION LANGUAGE

SELECT :- RETRIEVE SOME RECORDS FROM TABLE

INSERT :- CREATE A RECORD

UPDATE :- CHANGE OR MODIFY A RECORD

DELETE :- DELETE RECORDS

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DATA CONTROL LANGUAGE

GRANT  : GIVE PRIVILEGES TO USER

REVOKE : TAKE BACK PRIVILEGES GRANTED FROM USER

DATA DEFINITION LANGUAGE

CREATE : CREATE A TABLE, VIEW A TABLE, ALTER :- MODIFY EXISTING

TABLE DROP : DELETE AN ENTIRE TABLE

TRANSACTION CONTROL LANGUAGE

COMMIT: PERMANENTLY SAVE ANY TRANSACTION INTO DATABASE ROLLBACK : RESTORE THE DATABASE TO LAST COMMITTED STATE SAVE POINT: TEMPORARILY SAVE A TRANSACTION.
ELEMENTS OF DATABASE
Entity − An entity is a real-world entity having properties called attributes . Each attribute is defined by its set of values ca dlleodm ain. For example, in a college database, a student is considered as an entity. Student has various attributes
such as name, age, class, etc.
Relationsh ip − The logical group among relationship. is called. Relationships are mapped with entities in various ways. Mapping cardinalities define the number of connection between two entities.

Entity − An entity is a real-world entity having properties called attributes. Each attribute is defined by its set of values called domain. For example, in a college database, a student is considered as an entity. Student has various attributes such as name, age, class, etc.

Relationsh ip − The logical group among entities is called relationship. Relationships are mapped with entities in various ways. Mapping cardinalities define the number of connection between two entities.

Database Managements Question and Answer 

  • In the relational modes, cardinality is termed as:

(A) Number of tuples.            (B) Number of attributes.            (C) Number of tables.             (D) Number of constraints.

Ans : A

  •  The view of total database content is

(A) Conceptual view.      (B) Internal view.         (C) External view.                 (D) Physical View.

Ans: A

  • Architecture of the database can be viewed as

(A) two levels.         (B) four levels.               (C) three levels.              (D) one level.

Ans: Ans B

  • In E-R Diagram relationship type is represented by

(A) Ellipse      (B) Dashed ellipse      (C) Rectangle       (D) Diamond

Ans: D

  • An entity set that does not have sufficient attributes to form a primary key is a

strong entity set.     (B) weak entity set.            (C) simple entity set.               (D) primary entity

Ans: B

  • In an E-R diagram an entity set is represented by a

(A) rectangle.                 (B) ellipse.           (C) diamond box.                  (D) circle.

Ans: A

  • The statement in SQL which allows to change the definition of a table is

(A) Alter.         (B) Update.           (C) Create.              (D) select.

Ans: A

  •  Which database level is closest to the users?

(A) External            (B) Internal               (C) Physical              (D) Conceptual
Ans: A

  • In E-R Diagram derived attribute are represented by

(A) Ellipse                (B) Dashed ellipse         (C) Rectangle           (D) Triangle
Ans B

  • In E-R Diagram relationship type is represented by

(A) Ellipse       (B) Dashed ellipse      (C) Rectangle        (D) Diamond
Ans: D

  • An entity set that does not have sufficient attributes to form a primary key is a

(A) strong entity set.          (B) weak entity set.          (C) simple entity set.           (D) primary entity set.
Ans : B

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