Introduction to database system What is a Database system? What is a Database system? Data System Components Data System ComponentsDataHardwareSoftwareUser What is Database What is Database Benefits of Database Approach Benefits of Database Approach

Database System Database system is a computerized record-keeping system. It is a computerize system whose overall purpose is to store information and to allow users to retrieve and update that information on demand. Database system is a computerized record-keeping system. It is a computerize system whose overall purpose is to store information and to allow users to retrieve and update that information on demand. –Information is anything that is significant to the individual or organization concerned.

Data VS Information Data is used to refer to what is actually stored in the database Data is used to refer to what is actually stored in the database Information is used to refer to meaning of that data as understood by some user. Information is used to refer to meaning of that data as understood by some user.

Operations Adding new file to database Adding new file to database Inserting data into existing files Inserting data into existing files Retrieving data from existing files Retrieving data from existing files Deleting data from existing files Deleting data from existing files Changing data in existing files Changing data in existing files Removing existing files from the database Removing existing files from the database

Database System Components  Data  Hardware  Software  Users

Data Database System are available on machines that range from all the way from personal computers to the largest mainframe or clusters of mainframes. Database System are available on machines that range from all the way from personal computers to the largest mainframe or clusters of mainframes. In particular, tend to be multi-user; whereas on small machine tend to be singer user. In particular, tend to be multi-user; whereas on small machine tend to be singer user.  Single User system is a system in which at most one user can access the database at any given time.  Multi user system is a system in which many users can access the database at the same time.

The data in database – for large system- will be both integrated and shared. Integrated Integrated –Mean the database can be thought of as a unification of several district files, with any redundancy among those files partly or wholly eliminated Shared Shared –Mean the database can be shared among different users, in the sense that different users can have access to the same data, possible even at the same time (“Concurrent access”).

Hardware The hardware components of the system consist of The secondary storage volumes used to hold the stored data, together with the associated I/O devices, device controllers, and so forth. The secondary storage volumes used to hold the stored data, together with the associated I/O devices, device controllers, and so forth. The hardware processors and associated main memory that are used to supported the execution of the database system software The hardware processors and associated main memory that are used to supported the execution of the database system software

Software Database Management System (DBMS) Data => physically stored All request for access to the database are handle by the DBMS DBMS is thus shielding of database users from hardware level details Provides users with a perception of the database that is elevated somewhat above the hardware level details. Support user operations

Database Management System DBMS is a general purpose software system that facilitates the process of definition, construction, manipulating, and sharing databases among various users and applications. DBMS is a general purpose software system that facilitates the process of definition, construction, manipulating, and sharing databases among various users and applications. –Defining a database involves specifying the data types, structures, and constrains for the data to be stored in the database.

Manipulating a database includes such functions as querying the database to retrieve specific data, updating the database to reflect changes, and generating reports from data. Manipulating a database includes such functions as querying the database to retrieve specific data, updating the database to reflect changes, and generating reports from data. Sharing a database allows multiple users and programs to access the database concurrently. Sharing a database allows multiple users and programs to access the database concurrently. Other important functions Other important functions –Protection both system protection against hardware or software malfunction (crash) and Security protection against unauthorized or malicious access. –DBMS must be able to maintain the database System by allowing the system to evolve as requirements change over time.

User Application Programmer Application Programmer –Responsible for writing database application programs in some programming language End User End User –Access database interactively as just described, A given user can access the database via online application program or user query language

Database Designers Database Designers –Responsible for identifying the data to be stored in the database and for choosing appropriate structures to represent and store in database. –Undertaken before the database is actually implement. –It is responsibility of database designers to communicate with all database user to understand their requirements, and to come up with a design that meets users’ requirements. –Designer may be one of staff of Database Administrator (DBA) –Interact with each groups of users and develop views the database that meet the data and processing requirements of those groups. –Final database design must be capable of supporting the requirements of all user groups.

Database Administrators: responsible for authorizing access to the database, for coordinating and monitoring its use, and for acquiring software and hardware resource need Database Administrators: responsible for authorizing access to the database, for coordinating and monitoring its use, and for acquiring software and hardware resource need Defining the conceptual schema (Logical/conceptual Database Design) Defining the internal schema (Physical Database design) Liaising with users, to ensure that data they need is available and to write or help user to write the external schemas, using the applicable external DDL. Defining security and integrity constraints Defining dump/restore schemes Monitoring performance and responding to changing requirement.

Users/Programmers Application Programs/Queries Software to Process Quires/Programs Software to Access Stored Data DBMS Software StoredDatabase Stored Database Definition (Meta Data) DATABASE SYSTEM

Data Administration and Database Administrator Data Administration (DA) Data Administration (DA) –The person who take response the data in the enterprise –To decide what data should be stored in the database –Establish policies for maintaining and dealing with the data once it has been stored. –DA is a manager, not technician Database Administrator (DBA) Database Administrator (DBA) –Information technology profession –Create actual database and to put in place the technical controls need to enforce the various policy decision made by the data administrator.

What is a database By C.J. Date By C.J. Date “a Database is a collection of persistent data that is used by the application systems of some given enterprise” Elmasri & Navatha Elmasri & Navatha “Database is a collection of related data. –Data mean facts that can be recorded and that have implicit meaning.” –Database can be any size and varying complexity –Database may be generated and maintained manually or it may be computerized.

Why Database Compactness: no need for possible voluminous paper file. Compactness: no need for possible voluminous paper file. Speed: Machine can retrieve and update data faster than human Speed: Machine can retrieve and update data faster than human Less drudgery: maintaining files by hand is eliminated. Less drudgery: maintaining files by hand is eliminated. Currency: Accurate, up-to-date information is available on demand at any time. Currency: Accurate, up-to-date information is available on demand at any time. Protection: Data can be better protected against unintentional loss and unlawful Protection: Data can be better protected against unintentional loss and unlawful

Benefits of Database Approach The data can shared The data can shared Redundancy can be reduced/controlled Redundancy can be reduced/controlled Inconsistency can be avoided Inconsistency can be avoided Transaction support can be provided Transaction support can be provided Integrity can be maintained Integrity can be maintained Security can be enforced Security can be enforced Conflicting requirements can be balanced Conflicting requirements can be balanced Standard can be enforced Standard can be enforced

Controlling redundancy Controlling redundancy –Redundancy is storing the same data multiple times leads to several problems. Duplication effort Duplication effort Storage waste, when same data stored repeatedly Storage waste, when same data stored repeatedly File that represent same data may became inconsistent. File that represent same data may became inconsistent. –Database approach, the views of different user groups are integrated during database design. Logical data item in only one-place in database, Ensure redundancy, “controlled redundancy”.

Security Restricting Unauthorized Access Restricting Unauthorized Access – Multiple user share large database – most users will not be authorized to access all information in the database Example : KKU Registration Example : KKU Registration all database can see by DBA Students can see/manipulate only some part of their data some part of their data – –Type of operation must be controlled – –User/User group are given account number and passwords to access the data base. DBMS provide a security and authorization subsystem, DBA uses them to create account and to specify account restrict.

Example Fact(factcode, factname) Fact(factcode, factname) Dept(faccode, deptcode, deptname) Dept(faccode, deptcode, deptname) Student(id, name, address, factcode,factname) Student(id, name, address, factcode,factname) Subject(subjcode, subjname, credit) Subject(subjcode, subjname, credit) Teacher(tcode,tname,taddress,factcode,deptcode,….) Teacher(tcode,tname,taddress,factcode,deptcode,….) Grade(id,subjcode,year,sem,grade) Grade(id,subjcode,year,sem,grade) Etc. Etc.

Integrity Example Create table fact( factcode char(4), factname varchar2(30), primary key(factcode)); Example 2 Create table dept( factcode char(4), deptcode char(4), deptname varchar2(30), primary key(factcode,deptcode), foreign key (factcode) references fact(factcode));

view Create view studGrd as select id,name,subjcode,name,year,sem,grade from student,grade Create view studGrd as select id,name,subjcode,name,year,sem,grade from student,grade where stdent.id = grade.id where stdent.id = grade.id

Summary Define a database system and database components Define a database system and database components Database as a collection of related data, where data means recorded facts. Database as a collection of related data, where data means recorded facts. The benefic of the Database system The benefic of the Database system