WFM-6103: Hydrologic Information System (HIS) Akm Saiful Islam Lecture-5: Database Management System April-October, 2006 Institute of Water and Flood Management (IWFM) BUET Institute of Water and Flood Management (IWFM) Bangladesh University of Engineering and Technology (BUET) WFM 6103: hydrologic Information System © Dr. Akm Saiful IslamDr. Akm Saiful Islam

Outline Database Management System  Introduction to Databases  File System Vs. Databases  Advantages of using databases  Database Management System WFM 6103: hydrologic Information System © Dr. Akm Saiful IslamDr. Akm Saiful Islam

Introduction to Databases Information Systems process and manage data. Data Management involves “Capturing”, “Retrieval,” and “Storage” of data. Database Management Systems (DBMSs) are Computer systems that manage data in databases. Today’s DBMSs are based on sophisticated software and powerful computer hardware. Well known DBMS software includes ORACLE, Microsoft SQL Server, Sybase and MySQL(free download) among others. WFM 6103: hydrologic Information System © Dr. Akm Saiful IslamDr. Akm Saiful Islam

Data Storage: Terminology A collection of data entities is typically known as a file. An individual data entity is typically known as a record. Different attributes of a record are typically known as fields. A key is a field or a set of fields that uniquely identifies a record. Fields Records Key Product Category + Product Type + Year File (table) WFM 6103: hydrologic Information System © Dr. Akm Saiful IslamDr. Akm Saiful Islam

A Word on Keys A Key maybe: A field or set of fields that are used to identify the record. A Primary key is a minimal set of fields that uniquely identifies the record. A Foreign key is a field that is a primary key in another relation Primary Key Foreign Keys WFM 6103: hydrologic Information System © Dr. Akm Saiful IslamDr. Akm Saiful Islam

File Organisation Sequential Files records are stored in a fixed sequence records can only be read in that sequence, starting from the first record records can only be added at the end of the file (append) sequential files are not efficient Indexed Files Use an index to access records in a random fashion. Records can be sorted according to an attribute or preference. (e.g Alphabetically, Ascending, Descending, etc.) Indexed files are efficient, and faster to access. WFM 6103: hydrologic Information System © Dr. Akm Saiful IslamDr. Akm Saiful Islam

The File Systems Approach Redundant Data Storage. One file is used in each application. No data sharing. Cross-application transfers are difficult to manage and achieve. File Systems are rarely used for data processing anymore. General Ledger File Personnel File Production Planning File Inventory File Despatch File Order Entry File Invoicing File Payroll File WFM 6103: hydrologic Information System © Dr. Akm Saiful IslamDr. Akm Saiful Islam

The Database Approach Compactness. Data is stored in a single logical “place.” Data can be shared and related between applications Data transfer between applications is easier Used for a wide range of applications. General Ledger Personnel Production Planning Inventory Despatch Order Entry Invoicing Payroll WFM 6103: hydrologic Information System © Dr. Akm Saiful IslamDr. Akm Saiful Islam

Database Characteristics Amount  Database size depends on the number of records or files it contains. Complexity  Database complexity depends on the number of relations between the files. Volatility  A measure of the changes typically required in a given period of time. Immediacy  A measure of how rapidly changes must be made to data. WFM 6103: hydrologic Information System © Dr. Akm Saiful IslamDr. Akm Saiful Islam

Advantages of using a Database Approach Flexible Data Access. DBMSs have various tools to manipulate, query, or report data, such as Structured Query Language (SQL), and Report Generators. Hence:  Selected data is easily retrieved  A DBMS can accommodate different data views for different users Improved Data Integrity. Modern DBMSs consist of various tools and methods to:  ensure that data is correct, consistent, and current  verify data input and check whether data is ‘reasonable’. WFM 6103: hydrologic Information System © Dr. Akm Saiful IslamDr. Akm Saiful Islam

Advantages of DBs (continued) Improved Data Security. Tools such as password access, and encryption, ensure that data is not:  deliberately or accidentally damaged or changed  accessed without proper authorisation Data Independence.  Problems arising from the interdependence of data and programs are kept to a minimum. Reduced Data Redundancy.  Single version of the truth.  Efficient data storage.  Efficient time management of Hardware (CPU), programmer(s), analyst(s) and user(s).  Relational DBs use Normalisation to reduce data redundancy. WFM 6103: hydrologic Information System © Dr. Akm Saiful IslamDr. Akm Saiful Islam

Advantages of DBs (continued) Ability to Share and Relate Data.  Different user groups can use the same data.  Data in different (physical or logical) parts of the system can be related for a certain application. Standardisation of Data.  In general data items have common names and storage format. Increased Productivity.  The various tools reduce the complexity that is otherwise associated with DB maintenance when changes are required to the system. For example Law changes, Economy Changes, User Changes. WFM 6103: hydrologic Information System © Dr. Akm Saiful IslamDr. Akm Saiful Islam

Costs of Database Approach The implementation and use of DBMSs is normally associated with various costs. Such as:  Initial expenses involve planning costs, and consultancy fees.  Computer hardware costs.  Software costs.  Database Administrator costs, and staff training costs.  Conversion costs of an existing system.  Various operational costs. WFM 6103: hydrologic Information System © Dr. Akm Saiful IslamDr. Akm Saiful Islam

DataBase Management System (DBMS) A DBMS is a set of computer “programs” that control:  Database creation  Database maintenance  Database access A DBMS typically includes:  a Data Definition Language or DDL  a Data Manipulation Language or DML  a Query Language. Quite often this is Structured Query Language (SQL), or a derivative  a Report Generator WFM 6103: hydrologic Information System © Dr. Akm Saiful IslamDr. Akm Saiful Islam

The DBMS Manages the Interaction Between the End User and the Database Bangladesh University of Engineering and Technology © Dr. Akm Saiful IslamDr. Akm Saiful Islam

References Alex Berson, and Stephen J. Smith, Data Warehousing Data Mining, and OLAP, McGraw Hill, Chapters 1,13( inc.). ISBN C. J. Date, An Introduction to Database Systems, 3rd Ed. (or later), Addison-Wesley, Chapter 1. J. A. Senn, Analysis and Design of Information Systems, 2nd Ed. (or later), McGraw-Hill Chapter 12 (“Design of DB Interactions”). ISBN E. Turban J. Aronson, Decision Support Systems and Intelligent Systems, 5th Ed., Prentice-Hall, Chapter 4. ISBN WFM 6103: hydrologic Information System © Dr. Akm Saiful IslamDr. Akm Saiful Islam