The document discusses key concepts in entity-relationship modeling including: - Entity sets represent collections of similar real-world objects or entities with common attributes. Relationship sets define associations between two or more entities. - Attributes describe entities and can be simple, composite, single-valued, multivalued, or derived. - ER diagrams use standard notations to represent these concepts including entities as rectangles, relationships as diamonds, and different lines and crow's feet to denote attribute types and cardinalities in relationships.

1. B.Tech III Sem ‘A’
DATABASE MANAGEMENT
SYSTEMS
16 Jul 2019

2. DCL: Data Control Language
 GRANT : used to grant or give the privileges.
 REVOKE : used to avoid or object the privileges.
 COMMIT: used to save the data permanently.
 ROLLBACK : Used to revert changes in the
transactions since the last commit or rollback
command was issued

3. DCL: Commit
DELETE FROM
CUSTOMERS
WHERE AGE = 25;
SQL> COMMIT;

4. Rollback
 ROLLBACK command is the transactional
command used to undo transactions that have
not already been saved to the database.
 This command can only be used to undo
transactions since the last COMMIT or
ROLLBACK command was issued.
 DELETE FROM CUSTOMERS WHERE AGE =
25;

5. DCL : Grant & Revoke
create user korth identified by henry
 Connect as system/ora10g
GRANT SELECT, INSERT, UPDATE, DELETE
ON Emp_Det TO korth;
REVOKE DELETE ON Emp_details FROM

6. Student
Std_ID Name
Addr
Sec
DoB
Std_ID Name Addr Sec DoB
189X1A05XY Sree Sanfransisco A 01/01/1999
189X1A05XZ Sri Germany B+ 01/01/2000
ER Model Relational Model
Entity Relationship Model
represents the overall logical structure of a database.
The E-R data model employs three basic concepts: entity
sets, relationship sets, and attributes

7. Entity Sets
 Entity: Real-world object distinguishable from other
objects.
 An entity is described (in DB) using a set of attributes.
 Entity Set: A collection of similar entities.
E.g., all employees.
 All entities in an entity set have the same set of attributes.
 Each entity set has a key.
 Each attribute has a domain.

8. Entity Sets

9. Relationship Sets
 Relationship: Association among two or more
entities.
 A relationship set is a mathematical relation
among n  2 entities, each taken from entity sets
{(e1, e2, … en) | e1  E1, e2  E2, …, en 
En}
where (e1, e2, …, en) is a relationship

10. Relationship: Depositor

11. Relationship: Borrower

12. Attributes
 An entity is represented by a set of
attributes, that is descriptive properties
possessed by all members of an entity
set.Example:
customer = (customer_id, customer_name, customer_street,
customer_city )
loan = (loan_number, amount )

13. Attribute types
 Simple : Attribute is simple, if its value can not be divided into subparts.
For example Std_ID, Grade.
 Composite : Attribute is composite, if its value can be divided into
subparts. Ex: Name: First Name; Middle Name; Last Name
Address: H.No; street; city; pincode
 Single-valued : Attribute is a single-valued, if it has only one value for a
particular entity. PassportNo.
 Multivalued : Attribute is multivalued, if it has a set of values for a
particular entity. Ex: Phone number
 Derived: Attribute is a derived, if its value can be derived from the values
of other related attributes or entities. Ex: Age can be derived based on dob

15. ER Diagram Notations
________
_
Key
attribute
Derived
attribute

16. E-R Diagrams

17. Composite
Attributes
Multivalued
attributes
Derived Attribute
Relationship
Recursive
relationship

19. Cardinality Relationships
 The degree of a relationship = the number of
entity sets that participate in the relationship
 Mapping cardinality of a relationship
 1 –1
 1 – many
 many – 1
 Many-many

20. Mapping Cardinalities
One to one One to many
One-to-one: An entity in A is associated with at most one entity in B, and an
entity in B is associated with at most one entity in A
One-to-many: An entity in A is associated with any number in B. An entity in
B is associated with at most one entity in A

21. Mapping Cardinalities
Many to one Many to many
Many-to-one: An entity in A is associated with at most one entity in B. An entity
in B is associated with any number in A
Many-to-many: Entities in A and B are associated with any number from each other.

22. Supporting Slides