Relational Database Lecture, Lecture notes of Distributed Database Management Systems

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 Relational Databases

 Data Integrity Rules

 Dr. E.F. Codd

was a British scientist who worked for

IBM

invented the relational model for

database

management

 Relational Model

represents the database as a

collection of relations, with relations

pertaining to tables with rows and

columns

Dr. E.F. Codd

 Tuple

corresponds to a row of a table and an attribute

or field to a column

 Relation

is composed of fields (attributes) and tuples

are stored as tables in a relational database

system

 Attributes

are individual characteristics, and tuples form the

unordered set of characteristics that describe a

particular entity

 Primary key is also called a major key is the key field that serves as the unique identifier of a specific tuple in a relation is the field which occupies the first column within a certain relation  Domain is a pool of legal values for a given attribute  Foreign key is a field in one table whose values are constrained to be values of the primary key in another table is an attribute or a field of one relation whose values are required to match those of the primary key of another location

Emp_ID Emp_Name Emp_Address Emp_Age 00001 Melanie Novaliches 27 00002 Michael Cainta 26 00003 Phoebe Marikina 20 00004 Lomel Taguig 28 Item_ID Item_Name QTY 001 Shampoo 12 009 Soap 20 003 Electric fan 5 008 Toothbrush 15 Emp_ID Item_ID QTY 00001 001 6 00002 009 2 00003 003 1 00004 008 4 Foreign Keys Employee Relation Items Relation Sales-summary Relation

Data Integrity

 Data integrity

refers to the trustworthiness of system resources over their

entire life cycle

is “the representational faithfulness of information to the

true state of the object that the information represents,

where representational faithfulness is composed of four

essential qualities or core attributes: completeness,

currency / timeliness, accuracy / correctness and validity /

authorization”

 Types of Data Integrity Rules

Specific Integrity Rules

 are rules that apply to a particular database

General Integrity Rules

 are rules that apply to all relational database