The document provides an overview of the relational database model. It discusses how the relational model represents data in the form of tables (relations) and how a relational database management system (RDBMS) is based on this model. The key properties of the relational model are that each relation has a unique name, tuples are unique, attributes have the same domain, and attributes and tuples are not ordered. The document also describes schema diagrams, different types of keys like primary and foreign keys, and relational algebra operations like selection, projection, and joins that are used to query relational databases.

1. Relation Database Model
Unit 3
By
Anjan Baniya
Anjan Phuyal
Asis Subedi
Prakash Ghimire
Niraj Giri

2. Introduction to Relational Model
• The relational model is the theoretical basis of relational databases.
• The relational model of data is based on the concepts of relations.
• A “Relation” is a mathematical concept based on the ideas of sets.
• The Relational Model was purposed by Edgar Frank Codd for IBM in
1970 to model data in the form of relations or tables.
• Relational Model represents how data is stored in Relational
Databases. A relational database stores data in the form of
relations(tables).

3. What is RDBMS?
• RDBMS stands for Relational Database Management System. RDBMS
is the basic for SQL and for all modern database system like MS SQL
Server,IBM,DB2,Oracle,mysql and Microsoft access.
• A Relational database management system(RDBMS) is a database
management system(DBMS) that is based on the relational model.

4. Properties of Relational Model
• Each Relation has unique name.
• Each Tuple /row is unique : No duplicate row (Each Row is called
Tuple)
• Entries in any column have the same domain.
• Each attributes has a unique name.
• Orders of the columns or rows is irrelevant. i.e. relations are
unordered.
• Each cell of relation contains exactly one value. i.e. attributes values
are required to be atomic.

5. Fig: Keywords used in Relational database model

6. Schema Diagram
• Schema diagram is a graphical representation of database schema
along with primary key and foreign key dependencies.
• In schema diagram, each relation is represented by box where
attributes are listed inside box and relation name is specified above it.
Fig: Schema Diagram

7. Keys
• It is an attributes or set of attributes that uniquely identifies any
record or row of data from the table.
• It is also used to establish and identify relationships between tables.
• Keys play an important role in the relational database.

8. Types of keys
1. Super key is a combination of all possible attributes that can
uniquely identify the row or tuple in the given relation.
2. Candidate key is an attribute or set of attributes that can uniquely
identify a tuple.
3. Primary key is one of the candidate key chosen to uniquely identify
the tuple in the relation.
4. Foreign key is a mechanism used to establish a relationship
between two tables. It is a column or a set of columns in one table
that refers to the primary key of another table.

9. 5. Composite key is the key that have more than one attributes.

10. Relational Algebra
• Relational Algebra is a procedural query language which takes a
relation as an input and generates a relation as an output.
• Relational Algebra is a language for expressing relational database
queries.
• It uses operators to perform queries. An operator can be either unary
and binary.

11. Types of Operation in Relational Algebra
• Basic operations:
1. Selection (σ) Selects a subset of rows from relation.
2. Projection (π) Selects a subset of columns from relation.
3. Cross-product (×) Allows us to combine two relations.
4. Set-difference (−) Tuples in relation 1, but not in relation 2.
5. Union (U) Tuples in relation 1 and in relation 2.
6. Rename( ρ) Use new name for the Tables or fields.
• Additional operations:
1. Intersection (∩), join, division(÷): Not essential, but (very!) useful.

12. Types of Join
• Inner join: Contains
only those tuples that
satisfy the matching
condition

13. • Outer join: Contains matching
tuples that satisfy the matching
condition, along with some or all
tuples that do not satisfy the
matching conditions. Contains all
rows from either one or both
relation.
1. Left Outer join:
Left relation tuples will always be in
result whether the value is matched
or not.
2. Right outer join:
Right relation tuples will always be
in result whether the value is
matched or not.
3. Full Outer Join:
Tuples from both relations are
present in result whether the value
is matched or
not.

14. Thank You