• Join over 1.2 million students every month
  • Accelerate your learning by 29%
  • Unlimited access from just £6.99 per month

Features of database design

Extracts from this document...


´╗┐Database Design P1, M1 Unit 18 ? Database Design ________________ Contents Understanding the features of a database???????????????.????????2 Relational databases?????????????????????????????.????2 ? 4 Primary and Foreign Keys??????????????????????????????3 ? 4 Referential integrity???????????????????????????????????..4 Types of relationships????????????????..??????????????????5 Understanding the features of Databases A database is basically a collection of data that can include information on people for example names, telephone number or address. It could also include information on things such as the quantities of something, the status or location. Normally a database is organised by fields, records and files. A field is a column; a record is a row; and a file is a complete set of records. A good example of this is a telephone book apart not being a file it does contain a list of records with each normally or at least commonly consisting of three fields which are the name, address and phone number. A second example of a database or at least what can be used to make a database is the software Microsoft Excel, It contains columns and rows which make it a good choice for making a simple database. Below is an example of a Microsoft Excel database ? This is a database that shows students that are enrolled at a collage. There are many forms of databases the two examples above are two of the more well-known ones. ...read more.


Tables - The tables in a relational database is set out in rows and columns. For an example of a table, the image above shows how the table is set out with the fields, rows and colons. A table is also just another term for relations. Primary Key and Foreign Key The primary key is what sets up the relationships within the database. The primary key must be unique so the attribute must not repeat which means it will normally be a number of some kind for example if the Table was to keep a record for students the student ID would be used as no student will have the same ID as another student. The primary key defines the relationship with multiple tables by becoming a foreign key in the next table so they link, the foreign key will remain the primary key in the first table. I will use the same example as above to show primary and foreign keys. This is a one-to-many relationship Here you can see the Primary keys in bold are ?Customer ID? for the customers table, ?OrderID? for the orders table and for the order details table the key is ?ProductID? For the relationship to work the primary key must be in the next table and be a foreign key, this is what gives the database its referential integrity. ...read more.


A one-to-many relationship is created if only one of the columns is a primary key. Many-To-Many Relationships ? In a many-to-many relationship a row in ?Table A? will have more than one matching row in ?Table B? and the same will be said the one other way round as in ?Table B? will have more than one matching row in ?Table A?. This is possible by creating a third table called a junction table where the primary key consists of the foreign keys from the first two tables. For example, the Authors table and the Titles table have a many-to-many relationship that is defined by a one-to-many relationship from each of these tables to the TitleAuthors table. The primary key of the TitleAuthors table is the combination of the author?s table?s primary key column and the Titles table?s primary key One-To-One Relationships ? In a one-to-one relationship a row in ?Table A? will only have one matching row in ?Table B?. A one-to-one relationship happens is both of the related columns are primary keys. This is the relationship that gets used the least because most information that is related with the same primary key would most commonly be in the same table. Some of the reasons a one-to-one relationship is to be able to divide a table with many columns or store data that is not going to be used for long and can deleted easily. Benjamin Milner ...read more.

The above preview is unformatted text

This student written piece of work is one of many that can be found in our AS and A Level Information Systems and Communication section.

Found what you're looking for?

  • Start learning 29% faster today
  • 150,000+ documents available
  • Just £6.99 a month

Not the one? Search for your essay title...
  • Join over 1.2 million students every month
  • Accelerate your learning by 29%
  • Unlimited access from just £6.99 per month

See related essaysSee related essays

Related AS and A Level Information Systems and Communication essays

  1. Data Processing Task. Mr Peters, the man who runs this particular Samsung store ...

    This is achieved by in the criteria for OrderID, entering [Enter OrderID] Product by Colour: This is a parameter query which asks you to enter a colour. This is achieved by in the criteria for colour, entering, [enter colour]. This query is useful as you may have already decided on

  2. User Guide to my minibus hire database.

    If in a case there is a customer which has the same first name and surname then you can simply click the "Search Surname" button which will prompt the user to enter the surname and the postcode od the

  1. Health Book

    Steam's 'Steam Cloud' feature is one of its major features attracting a lot of attention and being one of the foundations it is succeeding in the gaming industry. This feature allows gamers to upload their personalized settings, game saves and gamer profiles to an offshore central server, giving the gamer

  2. Employee attributes and their value

    Their employees have a bigger workload shared by a smaller number of employees. An employee who is lazier than the others will hold back the progress of the company. There is only 1 financial manager in IT services. He has to deal with the financial matters himself and get the job done.

  1. Database Analysis & Design

    A relational database is a selection of tables of fields related by relationships. For example, a data set containing all the real estate transactions in a town can be grouped by the year the transaction occurred; or it can be grouped by the sale price of the transaction; or it

  2. Website Design, Creation and Evaluation

    This will require the creation of a Maintenance Plan. 1.2 Action Plan For this assignment I am going to create an action plan which will help me organise the progress of the project. This will allow me to easily manage my time much more efficiently and ultimately benefit the project.

  1. The different aspects of the design of my website for Hatch end cars.

    The diagrams below show the hierarchy of each of the data elements on the main menu. These sets out what screens appear when each of the buttons are clicked on. ENTITIES From the interview carried out and analysis of the system, I found out the various entities data is stored

  2. Evaluation of the database

    I detailed in the user documentation how graphs could easily be created in step-by-step form and tested that they could be successfully created. * An interface page with the school logo must be used to incorporate school image. I did create an interface page and included the school logo on it.

  • Over 160,000 pieces
    of student written work
  • Annotated by
    experienced teachers
  • Ideas and feedback to
    improve your own work