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Understanding The Components Of Access
Tue 3rd August 2010
The first object which is most important as all other objects use it is a table. Imagine an Excel spread sheet containing rows and rows of data. This is similar to a table as it is basically a collection of rows or records stored in a tabular format. In good database design there are usually more than one table with related data split into different tables. As an example, think of a company which sells toys online and need a database to do it. One table contains all information relating to the customer such as the first name, last name, address and telephone number. This is called the customer table. Another table contains all information relating to each different toy we are selling called the toy table. There is one record per toy with all information required on it such as warehouse number and colour. There is a final table relating to each sale we make called the sales table. This table contains all the information relating to the sale such as the date of sale and total sale value.
We link the tables together so that each sale is linked to a customer and a toy. If a customer makes many sales then their record can be linked over and over again to different sales records. This avoids the danger of repetition in the database. The reason we do not put everything into one table is to avoid this possibility of repetition, which can be problematic for several reasons. If a customer changes an address then we would have to update the customer details over and over again. There is also a chance that user error could cause spelling mistakes meaning mismatched records. If there is only one record for the customer then we only need to change it once, in one place. Each sale would need one row with the customer and the toy in it and these details may be repeated over and over again. Instead the customer information is only in the database once and when a sale is made the customer is linked to the sale record. It can be linked over and over again to many different sales records, but the information on the customer is only ever present in the database once.
Once all the tables are formed and the data entered, we would like the users to be able to enter the data in a user friendly front end. This will prevent them having to go directly into the tables to add data and can stop mistakes happening. We use forms as an extra layer over the tables. If you have a house with a front door that opens directly onto the living room, you may not like everyone who comes to the door having a good view of the inside of your house. For safety and security you build a front porch as an extra layer. A form is like this, it is still a doorway to the data, but allows users to enter data safely without accidentally deleting hundreds of records. It will have boxes to enter sale information and a drop down box so the user can pick the customer and toy automatically. The data is then entered correctly into the tables automatically by Access.
At the end of the month the manager asks us for a total of all sales for the month. Access allows us to create queries, which is basically a way of saying 'take all records between this date and that date and tell me the total in the sales value column.' There are many different kinds of queries including all sorts of parameters based on any present field. You can create totals or averages based on the sales area or the sales person, there is very little limitation on the queries provided the data is present in the tables.
Having sent the manager a total value and a spread sheet with all the details, he comes back and says it looks boring so can we jazz it up a bit as he wants to present the information at a monthly sales meeting. This can be done using reports. A report is based on a query so will contain the same information. Instead of just giving us a list of all the records or the total value we requested, we can put all the information arranged on a lovely colourful report and add various graphics such as graphs and logos. Reports are really about the presentation of the data collected.
These are the main objects that a novice will use. An advanced user may learn macros which are similar to the ones in Excel and Access. If you repeatedly perform several things in one go such as opening the database, opening the entry sales form and going to the last record then a macro can be recorded to save time. This will allow you to tell access to automatically do this so that when you open the database it is already set up for you to begin work. Macros can be attached to buttons on a form such to do things such as save record, go to the last record and many other things.
The last object is a module. Modules are really for advanced users as they require knowledge of VBA. This is a simple programming language which can be used to create new things for the database to do which are not already set up. There are many examples of these modules on line. To begin examining these objects you can use the template database called Northwind which already has tables set up containing sample data.
Author is a freelance copywriter. For more information on access+training, please visit https://www.stl-training.co.uk
Original article appears here:
https://www.stl-training.co.uk/article-1047-understanding-components-access.html
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