Presentation on theme: "Databases. The contents of databases often form the basis on which business decisions are made A considerable proportion of worldwide computer resources."— Presentation transcript:
The contents of databases often form the basis on which business decisions are made A considerable proportion of worldwide computer resources and programming activity are devoted to database applications Databases are the foundation for many types of applications: accounting, transaction systems, Management information systems (MIS), Executive Information Systems (EIS), data warehouses, document management, expert systems, etc.
Early data processing From the 20's through the 50's electromechanical machines handling punched cards were the mainstay of business data processing. IBM punched card shuffler
Magnetic media 9-track tape drive (sequential device) 300MB IBM 2302 disk drive (random-access device) When high-capacity random-access data storage devices (such as disk drives) and sorting and indexing methods became available, searching for a particular record became much faster.
Whatever the data storage and retrieval mechanism used, the fundamental element of a database is a TABLE. A table is a database object that consists of a collection of rows (records) that have an identical collection of properties. A record has several fields. Each field is devoted to one one property. Each record is uniquely identified with a primary key (the first field)
Flat-file databases A single table database Suitable for contact lists but problematic when records are expanded with more data, like customers expanded with sales. When information like customer, orders, salesperson, salesperson data must be included, a flat-file database will create repeating groups and inefficient storage.
Problem with flat-file databases = repeating groups Table Customers Table Orders The solution is a split-up into related tables, linked through Customer ID
The relational model Developed in 1970 by Dr. E. F. Codd Records are linked by relations between attribute values; a relation consists of a linkage between records in two tables that have identical attribute values. Revolutionised the database world, and is the dominant model today.
RDB Dublicate data among tables, but not within a table. Data in relational tables is independent of the methods used by the database management system to manipulate the records
RDB Tables in a RDB must follow certain rules, called the normal forms or normalisation. Certain data integrity rules exist for ensure that the database remains correct and complete at all times. A query is a communication to the database, such as a request for data, insertion of new data, change of structure, etc. Queries to a DRB are predominantly with Structured Query Language (SQL). Everyday users will not encounter SQL when using a database system, queries are normally pre-defined in the front-end application on the users desktop.
RDB SQL can define or create databases through action queries, e.g. CREATE TABLE or create new record entries with INSERT. SQL reserved words and syntax is defined in an ANSI standard Partial syntax of SQL query:
Some classic databases... In the 1960s Committee for Data System Languages (CODASYL) databases solved the problem with repeating groups through system of pointers. CODASYL databases and COBOL remain in use today on some mainframe systems today. dBase, Foxpro and Paradox were popular relational database programs for the PC in 1980s. dBase programming and query language was xBase and tables were stored as individual directories on disk.
RDBMS A Relational Database Management System (RDBMS) is an integrated set of programs used to define, update and control the database The RDBMS is the engine handing the data in the database tables
RDBMS IBM AS/400 series, sometimes with DB2 RDBMS preinstalled Main-frame and mid-range systems often has integrated RDBMS. Such native support gives a stable platform for creating and running various business applications
Centralized computing (before the PC)
In a client-server networking environment a central machine serves a number of clients (PCs). The shared database and database engine will be located on the server, while a front- end program is located on each desktop.
Client-server The philosophy in the client/server implementation is, you should offload database processing to the server. Therefore, the database engine should accept SQL requests from the client and execute them totally on the server, returning only the answer set to the client requestor. Network traffic will therefore be minimized. The RDBMS can handle large amounts of data and also automatically enforces certain data integrity and data security policies for multiple users.
MIS A Management Information System (MIS) generates management information for monitoring performance, maintaining coordination, and providing background information about the organization's operation MIS as a concept has merged with IS over the last decade, so that MIS now may designate the total Information System of the organisation. MIS Information Services IS Data Processing Information Department ?
MIS Databases applications are used for all manner of transaction handling, processing orders, invoices, parking tickets, etc. Management Information Systems (MIS) are supplying high-level business information to management.
Other types of DB-bases IS Decision Support System (DSS): Designed to support decision-making processes involving semi-structured or unstructured problems. DSS are most effective on tactical level of organisation (engineers,planners, etc.) Executive Information System (EIS). An MIS with DSS characteristics for executive decision support Expert System. Interactive case-based reasoning system that responds to questions, requests clarification and gives recommendations. Data Warehouse
Commercial Enterprise Systems ES allow companies to replace their existing information systems, which are often incompatible with one another, with a single, integrated system ES are off-the-shelf solutions/products. Largest ES software company = Wellknown product = SAP/R3
Commercial Enterprise Systems A central database draws data from and feeds data into a series of modules supporting diverse company functions
Data in organisations Massive volume Dispersed Difficult to access Badly integrated Complex data structures Not suitable for high level business queries Data in organisations tend to be spread over several databases and therefore tend to have the following characteristics:
What is a Data Warehouse? A single, complete and consistent source of data obtained from a variety of sources and made available to end users in a way that they can understand and use in a business context DW form a framework in which to perform data mining in the organisations information. (looking for gold nuggets of information/trends with strategic importance) Separate from the operational systems in the enterprise and populated by data from these systems. It therefore does not burden the operational systems, but rather sits on top of whatever systems provide data for the warehouse
Data Warehouse Mining Traditional database queries are typified by relatively simple questions. Data mining, on the other hand, through the use of specific algorithms or search "engines", attempts to source out discernable patterns and trends in the data and infers rules from these patterns. With these rules or functions, the user is then able to support, review and examine decisions in some related business or scientific area