 To provide you with an overview of the aspects that make up a relational database.  This includes: › Tables › Records › Fields › Data types › Keys › Composite primary key › Secondary key › Entities › Data dictionary › Parameter queries

 Imagine a database is a filing cabinet.  Each drawer stores information about a particular thing.

 Imagine a database is a filing cabinet.  Each drawer stores information about a particular thing.

 These are attributes that are designed as an alternate means of accessing data.  This attribute is not necessarily unique either.  For example, a library my use ISBN numbers as a primary key, but they may also store the book’s Dewey number.  You could still use the Dewey Decimal System to find a book but the database might not use this as a primary key.  This is because they may use the same Dewey number for a different book if it is located on a different floor.

ISBN: DDS: ISBN: DDS: Floor 2: A2 Revision Floor 1: AS Revision The library has two floors. The first floor is used to store books relating to AS subjects. The second floor is used to store books relating to A2 subjects. Each subject has a main code. ICT is 150, Maths is 151 etc. Each subject has a number of books.

 Whenever you create a database you need to keep a second ‘database’ which stores data about the structure and contents of the main database.  It should include data about: › What tables the database has and what their relationship to other tables is (more on relationships later). › The structure of each field › Validation rules › The number of records being saved › Etc…

 We know that tables store data…and in some database applications, such as MS Access, you can do some basic sorting (e.g. alphabetical).  But sometimes you need to find certain data based on different criteria.  For example, an internet service provider may want to find all customers who have not paid their bills yet.  They could then go on to filter these results further by looking for all customers who have had their first warning and still not paid.

A query can be used to find, sort and filter data. This data can then be used to find new data, e.g. total number of outstanding payments. It can also be used for things like mail merge, e.g. sending second warnings to customers.

 A simple queries uses one criteria value, for example: › Find all male students.  A complex query uses two more criteria values, for example: › Find all male students who were born after 1995.

 A parameter allows you to dynamically query data.  They allow you to cut down on the number of queries you have to create.  For example, you may have one query which finds all male students and another query that finds all female students.  If you create a parameter query you could have the query ask you what criteria to use. › If you type in Male it will find all male results. › If you type in Female it will find all female results.