Introduction to Database Systems Lecture 2 PDF

Introduction to Database Systems Lec #2  Agenda  Traditional File Systems  Database Approach  Advantages of Using DBMS 2  Traditional File Systems ▸Before the existence of computer: ▹The manual file system was used to maintain the data and records....

Introduction to Database Systems Lec #2  Agenda  Traditional File Systems  Database Approach  Advantages of Using DBMS 2  Traditional File Systems ▸Before the existence of computer: ▹The manual file system was used to maintain the data and records. ▹Files were used to store the data and it also makes it easier to find any sort of information from the files. ▸To overcome the problems of the manual file system: ▹Traditional File System was introduced which was entirely a computer-based system where all information were stored in different files on the computer. ▹It also stores the whole data in a manner that it becomes easy for the departments of the large industries have their different files, but it forms redundancy of the data. 3  Traditional File Systems ▸The data of the students stored in three different files such as: ▹a separate data file for Library, ▹the second one is for examinations, and ▹the last one is for registration. ▸All these files create duplicate data such as the student number, their name, and phone numbers. 16 Figure: Example of college data  Traditional File Systems 17 Figure: Example of library loan system  Traditional File Systems ▸Advantages: ▹Simple functionality that fits the needs of small businesses and home users ▹Less expensive ▸Disadvantages: ▹Does not support multi-User access ▹Limited to small organizations ▹Limited functionality (i.e. no support for complicated transactions, recovery, etc). ▹Decentralization of data 6 ▹Redundancy and Integrity issues  Database Approach ▸All data is stored in a single database. ▸The database will be physically stored in a set of files, but users and applications do not need to know anything about the physical storage. ▸Relationships between sets of data are represented in the database. ▸The description of database, including relationships is stored with actual data; this to enable the database management system (DBMS) to retrieve information from the database and to store new data in the database. ▸The applications do not directly access the database; instead, they pass requests to the DBMS to retrieve or store data. 7  Database Approach 20 Figure : Example of library loan database system  Traditional File Approach VS. Database Approach ▸In simple terms, a File Management System (FMS) is a Database Management System that allows access to single files or tables at a time. ▸FMS’s accommodate flat files that have no relation to other files. ▸The FMS was the predecessor for the Database Management System (DBMS), which allows access to multiple files or tables at a time. Figure : FMS vs. BBMS 9  Advantages of Using DBMS ▸Controlling redundancy in data storage and in development and maintenance efforts. ▸Sharing of data among multiple users. ▸Restricting unauthorized access to data. ▸Providing Storage Structures for efficient Query Processing ▸Data independence provides an abstract view of the data that hides the details data representation and storage. 10  Advantages of Using DBMS ▸Efficient Data Access where variety of techniques are used to store and retrieve data. ▸Data integrity we can ensure data integrity if the data is always enforced through integrity constraint ▸Data administration deals with the modeling of the data and treats data as an organizational resource. ▸Concurrent Access and crash recovery ensures concurrent access of the data in such a way that the data is being accessed by only one user a time. Also protects the system from crashes. ▸Reduced Application Development time supports all the important functions 11 that are common to many applications.  Database Users ▸Users may be divided into: ▹Actors on the Scene: those who use and control the content, and ▹Workers Behind the Scene: those who enable the database to be developed and the DBMS software to be designed and implemented. 12