Database structure - Callum pilling

Database structure - Callum pilling

1. A database is a system for managing a collection of data. Data about a particular type of thing – for example, customers or products – is stored in a table . You can think of a table as a grid. Every row in the table holds information about a single item; this is also called a record . Every column holds information about a property of the items in the table, such as a customer’s name or an item’s price – these properties are called fi elds .

2. Data base

   • Every field (column) in a database is set up to hold a certain type of data. The main data types are as follows:
     • text (also called characters or strings ): sequences of letters, numbers and other symbols. Someone’s name would be a text fi eld. A fi eld that can accept multi-line text is often called a memo fi eld.
       • number: represents a numerical value. A product’s price or the number of items left in stock would be stored as numbers. This would enable you to produce a report summing up the prices of all the products you had sold, which wouldn’t be possible if they were stored as text.
         • date/time: stores dates or a combination of dates and times.
           • Logical (also called Boolean or Yes/no ): represents a value that is either true or false. For example, when a customer opens an account with an online company, they might be asked whether they are happy to receive marketing material. Their answer could be stored in a logical fi eld (true if they are happy to receive marketing information, false if they are not).