1 DATABASE By Mr. Abdalla A. Shaame

 What is a database?  The main characters of a database system  The basic database design method  The entity-relationship data model for application modeling 2

3 Types of databases traditional multimedia - pictures, video, sound Scientific database - GIS: maps, weather, satellite images - biological database: DNA sequence analysis warehouse, OLAP - analysis, decision making real-time, active databases - industrial processes deductive databases - combination of inference and databases

4 Database collection of related data represents some aspect of the real world built with a specific purpose in mind could be anywhere - notebook, spreadsheet, Access, Oracle, … could be manual / could be computerized Data known and recordable facts name, phone number, address, grade,...

A database system is composed of four components;  Data  Hardware  Software  Users 5

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7 Database Management System (DBMS) collection of software facilitating the definition, construction and manipulation of databases Definition record structure data elements names data types constraints etc Construction create database files populate the database with records Manipulation querying updating

8 Database Management System (DBMS) collection of software facilitating the definition, construction and manipulation of databases Users/ actors Request manager Storage manager Meta data Stored database DBMS

9 Sample database Student Name StNo Class Major Smith 17 1 CS Brown 8 2 CS Course CName CNo CrHrs Dept Database CS C CS Section SId CNo Semester Yr Instructor Spring 2000 Smith Winter 2000 Smith Spring 2000 Jones Grades StNo Sid Grade A B file1file2 file3 file4

10 Characteristics of the Database approach single repository of data sharable by multiple users concurrency control transaction control self-describing - system catalogue contains meta data program-data independence some changes to the database are transparent to programs/users multiple views of data - to support individual needs of programs/users

11 Database Actors Database Administrator (DBA) -authorizing access to the database -coordinating and monitoring its use -aquiring software and hardware as needed -solving problems such as breach of security or poor system performance Database Designers/Modelers -identifying the data to be stored -choosing appropriate data structure End-users -access to the database: querying, updating, generating reports Software Engineers -developing application programs

12 Advantages of the Database approach (capabilities we would look for in a DBMS) controlled redundancy database design integrates different user data needs performance tuning may lead to replicated data Sharing of the data controlled/authorized access to data Ensure integrity of the data backup and recovery

13 Implications of the Database approach standards enforcement DBA can enforce standard naming conventions, etc reduced application development time adding new functionality to an existing database is “easy” flexibility adding new data and making some types of changes is “easy” up-to-date information - due to sharable characteristic economies of scale - due to sharable resources the whole organization can make one investment

14 When not to use a DBMS overhead costs are too great high initial investment data and applications are simple, well-defined, not expected to change stringent real-time constraints multi-user environment not needed

15 Database design let’s jump ahead to see this Grades Student Delivery 1 N Course Section N M

16 Database design let’s jump ahead to see this Grades Name Major Student StNo Class Delivery Course Section 1 N N M

17 Database design let’s jump ahead to see this Grades Name Major CName CNo Student StNo Class Delivery Course Section CrHrs Dept 1 N N M

18 Database design let’s jump ahead to see this Grades Name Major CName CNo Instructor Semester Year SId Student StNo Class Delivery Course Section CrHrs Dept N 1 NM

19 Database design let’s jump ahead to see this grade Grades Name Major CName CNo Instructor Semester Year SId Student StNo Class Delivery Course Section CrHrs Dept 1 N N M

20 employee department project dependent With attributes, etc: works for manages works on dependents of controls supervision bdate ssn name lname minit fname sex address salary birthdatenamesex relationship name numberlocation name numberlocation number of employees startdate hours N supervisor supervisee M N 1 1 N N degree 1 N

21 ER-to-Relational mapping 1. Create a relation for each strong entity type 2. Create a relation for each weak entity type include primary key of owner (an FK - foreign key) owner’s PK + partial key becomes PK 3. For each binary 1:1 relationship choose an entity and include the other’s PK in it as an FK. Include any attributes of the relationship 4. For each binary 1:n relationship, choose the n-side entity and include an FK of the other entity. Include any attributes of the relationship

22 5.For each binary M:N relationship, create a relation for the relationship include PKs of both participating entities and any attributes of the relationship PK is the concatenation of the participating entity PKs 6. For each multivalued attribute create a new relation include the PK attributes of the entity type PK is the PK of the entity type and the multivalued attribute 7. For each n-ary relationship, create a relation for the relationship include PKs of all participating entities and any attributes of the relationship PK may be the concatenation of the participating entity PKs