Lecture 1 - Introduction to the module & databases Emma-Jane Phillips Pandon 122. Relational Databases. Relational Databases. Welcome to the module How the module is organized and assessed What YOU need to do to pass this module Database fundamentals Summary.
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Pandon 122Relational Databases
The new regulation means that students MUST ATTEMPT ALL ASSESSMENT on their module. They cannot pass the module if they do not attempt all parts of it. This means even if they have 80% overall, if they have missed one part worth 5% of the module, they will not be able to pass the module. This will come into effect for all assessments this academic year 2009-2010.New Assessment regulation
The quick brown fox jumped over the lazy fox
26th August 1972
There needs to be a special piece of software to manage the database if the benefits are to be obtained
The DBMS is covered in later sessions
In reality databases hold only certain types of data in a true relational database form, we are looking at RDB in this course and although we need to be aware to the theoretical possibilities we are mainly focusing on the real world situation.
As mentioned, all the data in a database is held in a cluster of similar data (normally similar MEANING not DATATYPE)What is a relation/table?
In the above table, all the data would be the type of data you may find in a CUSTOMER table, we have the name, address, etc. Note: not all data is entered, some data may be optional.
Data can be of different formats or data types in a database, some data though may be held but not available to have all actions on them for example, a picture can be added or deleted but not updates (you can not change Esmerelda’s hat for a bonnet etc) it is more common to find the data above held as .........
In the above table we can see that the image has no longer been embedded into the table, instead the location of the image is displayed, this data would be used to locate the image if it is needed but the data itself remains true to the relational principles.
There are various books or papers that discuss databases, and it is often confusing to find that 2 different sets of terms are used, one set RELATIONAL terminology and another SQL terminology.
3 tables: student hold the student personal data, programme includes data on the different programme structures and module contains information on the different modules. The tables each hold data that will stand in isolation, if we need info on the BIS programme of the Games programme we look in the programme table but also the tables relate to each other, a student is enrolled on a programme and each programme has a number of modules associated with it and modules may run on a number of different programmes
It is important that relationships between data are clear and understood in order to get the most out of the database and its data
1 – many
Many – Many
1 – 1
Normally 1 – many are the types of relationships that we need to fosterRelationships
A company employees a number of people, the personal details such as name, address, salary and payroll number etc are held in the works database. Each employee works for a department and each department is responsible for a number of different projects.
What are the main clusters of data (this will give you the tables/relation)
What content will be in each of the identified tables/relation (this will give you the columns/attributes within the table/relation)
Think about how the different data relates to each otherTask (not included in your book so copy into your notes!)
Before next weeks lecture you are expected to read all the notes in the booklet that relate to this weeks lecture (up to page 17).
Next week we are going to look at the tables/relations in more detail, how they work, what additional elements we have to include in addition to the expected attributes and what limitations they have.Next .....