Welcome to our Presentation
Topic: E-R diagram & SQL
Presented by:
The roll of 20, 22, 23, 30 & 38
Batch: E-56
Dhaka International University (DIU)

Entity Relationship Diagram (ERD)
An Entity Relationship Diagram (ERD) is a snapshot of data
structures. An Entity Relationship Diagram shows entities
(tables) in a database and relationships between tables within
that database. For a good database design it is essential to
have an Entity Relationship Diagram.
There are three basic elements in ER-Diagrams:
 Entities are the "things" for which we want to store information.
An entity is a person, place, thing or event.
 Attributes are the data we want to collect for an entity.
 Relationships describe the relations between the entities.

Symbol used in E-R diagram
 Rectangles: Represent entity sets.
 Diamonds: Represent relationship sets.
 Lines: Link attributes to entity sets and entity sets to relationship sets.
 Ellipses: Represent attributes.
 Double ellipses: Represent multi-valued attributes.
 Dashed ellipses: Denote derived attributes.
 Underline: Indicates primary key attributes. (Describe later)

E-R Diagram With Composite,
Multi-valued and Derived
Attributes
Mapping Cardinality & Constraints
Mapping Cardinality:
 Express the number of entities to which
another entity can be associated via a
relationship set.
 Most useful in describing binary relationship
sets.
For a binary relationship set the mapping
cardinality must be one of the following types:
 One to many
 One to one
 Many to one
 Many to many
Cardinality & Constraints:
We express cardinality constraints by drawing
either a directed line (→), signifying “one,” or an
undirected line (—), signifying “many,” between
the relationship set and the entity set.

 One-to-One
 A customer is associated with at most one
loan via the relationship borrower
 A loan is associated with at most one
customer via borrower
 One-to- Many
 In the one-to-many relationship a loan is
associated with at most one customer via
borrower, a customer is associated with
several (including 0) loans via borrower

 Many-to-One
 In a many-to-one relationship a loan is
associated with several (including 0) customers
via borrower, a customer is associated with at
most one loan via borrower
 Many-to- Many
 A customer is associated with several (possibly 0)
loans via borrower
 A loan is associated with several (possibly 0)
customers via borrower

Alternative Notation for
Cardinality Limits
Participation of an Entity Set in a
Relationship Set
Keys
Primary Key – A primary is a column or set of columns in a table that uniquely identifies tuples
(rows) in that table.
Super Key – A super key is a set of one of more columns (attributes) to uniquely identify rows
in a table.
Candidate Key – A super key with no redundant attribute is known as candidate key.
Foreign Key – Foreign keys are the columns of a table that points to the primary key of another
table. They act as a cross-reference between tables.

Structured Query Language(SQL)
What is SQL?
SQL (pronounced "ess-que-el") stands for Structured Query Language.
SQL is used to communicate with a database. According to ANSI
(American National Standards Institute), it is the standard language for
relational database management systems. SQL statements are used to
perform tasks such as update data on a database, or retrieve data from a
database. Some common relational database management systems that
use SQL are:
 Oracle
 Microsoft SQL Server
 MySQL, etc. (We describe MySQL here.)
Although most database systems use SQL, most of them also have their
own additional proprietary extensions that are usually only used on their
system. However, the standard SQL commands such as "Select",
"Insert", "Update", "Delete", "Create", and "Drop" can be used to

MySQL
MySQL: MySQL is a fast, easy-to-use RDBMS being used for many small and big
businesses. MySQL is becoming so popular because of many good reasons :−
 MySQL is released under an open-source license. So we have nothing to pay to use it.
 MySQL is a very powerful program in its own right. It handles a large subset of the
functionality of the most expensive and powerful database packages.
 MySQL uses a standard form of the well-known SQL data language.
 MySQL works on many operating systems and with many languages including PHP,
PERL, C, C++, JAVA, etc.
 MySQL works very quickly and works well even with large data sets.
 MySQL is very friendly to PHP, the most appreciated language for web development.
 MySQL supports large databases, up to 50 million rows or more in a table. The default
file size limit for a table is 4GB, but you can increase this (if your operating system can
handle it) to a theoretical limit of 8 million terabytes (TB).
 MySQL is customizable. The open-source GPL license allows programmers to modify the
MySQL software to fit their own specific environments.

MySQL Commands
Create & Show database: Use database:
Create table:

MySQL Commands
Show table list: Show table structure:
Insert values in a table: Shows all data of a table:

MySQL Commands
We have already created a table to the name
of student to show the ALTER and SELECT
operation of MySQL database. The table is :-
Add address column into student table.
Drop address column from student table.
Drop primary key from student table.

MySQL Commands
Add primary key into student table. Select all data from student table.
Seelect only roll & name from student table.
Select roll & name where age > 18 from
student table.

MySQL Commands
AUTO_INCREMENT property into id field of test table. Define an initial value of id (AUTO_INCREMENT) field of
test table.
We have created two tables to the name of loan and borrower to show the Cartesian table operation of
MySQL database and inserted some data in those tables.

MySQL Commands
Cartesian table operation: Shows all data from loan
and borrower table where loan.loan_no is equal to
borrower.loan_no (and amount > 1500).
String Operation: We have created a table to the
name of customer to show the String operation of
MySQL database and inserted some data in the table.

String Operation
Find the name of all customer
whose name start with ‘IBR’
Find the name of all customer
whose name end with ‘him’
Find the name of all customer
whose name contain ‘man’
Find the name of all customer whose
name second character ‘b’
Find the name of all customer whose name start with ‘Mon’ and
end with ‘man’

Have you any question