Database concepts presentation version 2010 revised
- 1. Created by M Nodalo, Port Moresby International School for Year 11 Information Technology (T) - ACT/BSSS, revised 2010
- 2. Objective So that students will be able – to discuss the basic database concepts and terminologies – data, information, field, record, key field, computed fields, field length, data types, etc. To discuss the concept of relational database and flat-file database To discuss the concept of SQL (structured query language)
- 3. Data Vs. Information Data – raw fact or figures Example : Max Freeman 55,000 25 Information – data that have been processed to be meaningful to the user Example: K55,000 x .25 = K13,750 Max Freeman is a salesman who earned K55,000 sales for this month and therefore, receives 25% commission which is K13,750.
- 4. Stages of Processing Data Input processing Output data information• Calculating • Sorting • Classifying • Analysing • Summarising • reporting
- 5. What is a Database? An organised collection of data items that are related to a particular topic, purpose or activity Examples: a telephone directory, an address book, student class list
- 6. Databases can be stored Manually (in a filing cabinet with index cards, 3-ring binders, file folders) Electronically using a computer system (with suitable database software)
- 7. Manual databases - concerns Data duplication – same data on each file Effects of data duplication: More space is taken up by the files More work is needed to retrieve the information
- 8. Advantages of Computerised Databases over Paper files Easier to store large volume of information Easier to retrieve information quickly /flexibly Speed of information processing Versatility/flexibility in organising & reorganising information Easier to display, print & distribute information in a variety of ways Validation checks may be made on the data (done by a computer program)
- 9. Disadvantages of Computerised database over paper files Unable to access data when there’s a computer breakdown Ease of copying computer files; passwords needed for extra protection Extra cost & time to train people to use the database
- 10. Planning a Database Define the purpose of the database Determine the type of output reports List all the data items (determines the fields)
- 11. Database Structure Table – a collection of related records Record – a collection of data about a person or thing made up of one or more fields Field – a single piece of data or information common to all records file record Name: Venus Jackson Age: 27 Home Address: Gere-gere Ave., Boroko, NCD Gender: Female Job Position: Accounts Clerk Pay Rate/FN: 750.00 Years in Service: 5 fields Employee file
- 12. Example of a Database Telephone Directory Telephone Directory Name Address Phone Number Aldo,Mark East Boroko 323-2932 Amani,James Hohola 325-9022 Artona,Kathy Port Moresby 323-4325 records File/table name Field data Field name
- 13. Two parts of a field: 1. Field name – words that represent each field data or information, e.g. name, address, phone number, etc. 2. Field data – the actual data or information item stored in a field, e.g. Mary Jones, Boroko, 325-3423
- 14. Designing a Record Field names Type of data (text, numeric, date, boolean, image) Field length or size – the total number of characters allowed for a particular field Field description
- 15. Field length/size Should be designed to cope with the largest entry possible without reserving unnecessary disk space Too long field sizes – - will take up more space on the storage media (floppy/hard disk/CDs/flash drives) - takes longer to process
- 16. Types of Data Numeric – contains only numbers Character text – numbers, letters & other symbols can be entered Date – date is entered as 01/09/04 Logical (Boolean) – allows Y/N (yes/no) or T/F (true/false) Image/Picture
- 17. Key Field A field that may be used to search a file It makes a record unique from other records in the file e.g. student ID number, Book ID number, employee ID, customer code
- 18. Computed field Contain formulas similar to spreadsheet formula They display values calculated from values in other numeric fields Example: Net Pay may contain formula which calculates an employee’s net pay using Gross Pay and Tax fields
- 19. Field Name Data type Field size/length Description Sample database: Student file
- 20. Features of Computerised Databases Create fields Add and alter records Search for specific records Sort records Print reports
- 21. What is DBMS? DBMS – Database Management System A computer program that allows you to set up a database on computer. build a database add new data, delete or edit existing data search and extract specific data based on certain criteria (query) change/alter the structure of the data file sort and reorganise data display data on screen / print reports security of allowing certain people to access files
- 22. What is MS Access? An example of a DBMS which was developed by Microsoft Corporation.
- 23. Database Terms in Access Fields (columns) Records (rows) table – refers to a file in Access
- 24. Database Queries Issues the incompatibility of database languages created difficulty for people using different applications to access the same database E.F. Codd (IBM) – proposed the standardized structured English Query Language or what evolved as the SQL
- 25. Structured Query Language (SQL) Not a database management system Not a full-featured programming language like Java or C+. It is a sublanguage tailored for the database environment SQL statements – embedded inside computer programs such as COBOL, C or other programming languages SQL statements – understood by MS Acccess, MS SQL Server, DB2, Oracle, Sybase & other database programs
- 26. Structured Query Language (SQL) Combines database concepts of Tables/files Records (rows) Fields (columns) Mathematical concept of set See example on pages 234-235 (Chapter 7 Database Applications and Privacy Implications, Tomorrow’s Technology and You) – 7.1 The Language of Database Queries
- 27. Structured Query Language (SQL) Basic SQL statements – filters the records of a database to be able to extract only those records that meet specific criteria SQL statement format: SELECT (specify fields to extract) FROM (specify source – file name) WHERE (specify criteria or condition using appropriate comparison operators such as AND, OR, NOT, =, >, <, <>, >=, <=)
- 28. Types of Databases • Flat file database – uses only one file at a time Example: MS Excel – spreadsheet list • Relational database – consists of several files in which data can be accessed simultaneously Example: MS Access
- 29. Relational Database Relational database links some tables with certain data common with other tables.
- 30. Sources • Chapter 7 – Database Applications & Privacy Implications, Tomorrow’s Technology and You (8th ed) by G. Beekman & M. Quinn