Unit 18 - Database P1, M1

1008 WordsJun 22, 20135 Pages
Database Database, it is a place use to store lots of data. It can be seen as a filing cabinet. And database management system (DBMS) is software that specificity designs for managing the data in database such as create, update or delete them. General is including security, retrieval and backup features. User also allows using the data to create a report or share data with multi-user. MS Access is a database management system design by Microsoft. It offers user four important objects they are: * Table A Table is where you are organised and store data so you have to create the table before store any data. By creating table, you need to define few things, Fields name, Data type, and the Description. * Fields Name Fields…show more content…
* Data Redundancy – Relationships General a database has a lot of tables and some tables are related to each other so relationship is use to make the connection between two or more tables. It is a method to avoid excessive data and to ensure the data integrity. There have three types of relationships: * One to One For example, one employee only has one ID and one ID only for one employee. In many case, “One to One” relationship is for reduce the time to searching data. * One to Many Simply, “One to Many” means one thing or one person has many relations with other. For example, one department can have many employees. * Many to Many “Many to Many” is different with other two. To build “Many to Many” relationship you need to have at least three tables. It is because “Many to Many” cannot make the connection directly. For example, a student can choose many course but a course can have many student too so you cannot actually link them together. To link them, you will need a table to transfer data so the relationship will become “Many to One” and “One to Many”. * Normalisation It is a design method that used to avoid data redundancy and eliminate uncoordinated relationship. Normalisation has six stages to help with separate data which are UNF, 1NF, 2NF, 3NF, BCNF, 4NF and 5NF. * UNF is the first stage which is unnormalised; * 1NF is to remove the repeating groups; *
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