Learning Microsoft Access 2007 - Invoices

Learning Microsoft Access 2007By Greg Bowden

Guided Computer Tutorialswww.gct.com.au

Chapter 12

Setting up an Invoice System

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www.gct.com.au

© Greg Bowden

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© Guided Computer Tutorials 2008 12-1

Chapter

12Setting up an Invoice SystemTo fully understand the value of relational databases you need to create a detailed system. In this chapter you will setup an invoicing system for a computer mail order company, PC Direct, which sells computer peripherals through the mail. The invoice system will then be completed in the following three chapters. There are three main sections to the system, customers, products and the sales invoice.

In the creation of any database system you should do some careful planning. In general there are four steps that you should undertake.

1 Decide how many tables you think you might need.

2 Decide how the tables will be related to one another.

3 List the fields in each table trying to avoid having the same field in more than one table. Decide which fields will be the PRIMARY KEY and FOREIGN KEY fields to link the tables.

4 Decide what forms and/or reports (or printouts) are required.

In the case of PC Direct an initial TABLE RELATIONSHIP diagram might be:

The CUSTOMERS to INVOICE section of this structure forms a ONE TO MANY relationship. The one customer can have MANY invoices sent to them over time, but there will always be ONE customer on each invoice. So the customer table is the ONE side of the relationship and the INVOICE is the MANY side. We can set a relationship to link these two tables.

There is a problem with the link between the INVOICE and the PRODUCTS tables. The one invoice can contain many products and the one product can be included in many invoices. A relational database cannot cater for a MANY TO MANY relationship as you cannot set multiple PRIMARY or FOREIGN KEY fields in the one relationship.

A further problem exists, one invoice might contain a sale of 5 of a particular item, the next invoice might contain a sale of 2 of the same item. The company needs a way of adding these sales so that it knows how many items it has sold. So this initial TABLE RELATIONSHIP will need modification.

The easiest solution to these problems is to add a table between INVOICE and PRODUCTS. This table can store every item sold by the company as a single record allowing the company to keep track of every item sold. The new table can also provide data to the INVOICE table.

Customers Invoice Products

One to Many Many to Many

© Guided Computer Tutorials 200812-2

Learning Microsoft Access 2007

So a revised TABLE RELATIONSHIP diagram becomes:

The ONE invoice can have MANY items sold within it. The ONE product can be sold MANY times. By adding the LINE ITEMS table to the system a series of ONE TO MANY relationships are created and a relational database system can accommodate these.

The next step is to decide on the fields to be placed in each table. The following TABLE STRUCTURE diagram shows one possibility. Remember, we do not want to store data more than once (except for PRIMARY KEY or FOREIGN KEY fields).

The PRIMARY KEY and FOREIGN KEY fields need to be considered. In the previous diagram you would have see that CUSTOMER ID is used to link the CUSTOMERS and INVOICE tables, INVOICE NO is used to link the INVOICE and LINE ITEMS tables and PRODUCT ID is used to link the LINE ITEMS and PRODUCTS table. The INVOICE table is not directly linked to the PRODUCTS table, it will obtain values from the PRODUCTS table via the LINE ITEMS table.

The final consideration in the planning is what reports will be required. The following diagram shows some of the reports that could be made from the various tables. We will create some of these reports in the next chapter.

Customers Invoice Products

One to Many One to Many Link

Items Sold

One to Many

Customers Invoice Line Items ProductsCustomer ID Invoice No Invoice No Product IDTitle Customer ID Product ID Product NameFirst Name Date Sold Qty Sold Cost PriceLast Name Retail PriceOrganisation InstockStreet Reorder NumberSuburb LocationState

PostcodePhone

Fax

Customers Invoice Items Sold ProductsCustomer List Invoice Item Lists Product ListMailing Labels Monthly Totals

Item Totals

1

M

1M

M

1


12Setting up an Invoice System

Loading the Sample File

1 Load Microsoft Access and click on the OPEN icon in the OFFICE BUTTON, or close the current file and click on the OPEN icon in the OFFICE BUTTON.

2 Access the CHAPTER 12 folder of the ACCESS 2007 SUPPORT FILES and open the CHAPTER 12 file as an OPEN READ-ONLY file.

3 Click on the OFFICE BUTTON again, highlight SAVE AS and select ACCESS 2007 DATABASE.

4 Access your ACCESS STORAGE folder and save the file as CHAPTER 121.

A Looking at the Tables

The database has 3 tables at the moment, CUSTOMER DETAILS which stores data about the company’s customers, LINE ITEMS which stores details of each product sold and PRODUCT DETAILS which stores a list of the products that the company markets.

2 Close the CUSTOMER DETAILS table,

1 Open the CUSTOMER DETAILS table, set the view to DESIGN VIEW and notice that the CUSTOMER ID field has been set to the PRIMARY KEY field. The other fields store general information about the company’s customers.

3 Open the LINE ITEMS table, set the view to DESIGN VIEW and notice that there is no PRIMARY KEY field. It just stores basic details PRODUCT ID and QTY sold that the invoice will need.



NOTE: The LINE ITEMS table will record each line of the invoice. It will have two main purposes:

(A) to list each product sold as a separate record so that the company can calculate monthly sales and carry out stock checks.

(B) to provide product data to the invoice. If you look at the diagram at the centre of page 12-2 you will see that the PRODUCTS table is not directly connected to the INVOICE table so some data, such as Product Name and Retail Price, will need to be linked to the LINE ITEMS table via a relationship to the PRODUCTS table so that the INVOICE can display them.

4 Close the LINE ITEMS table.

6 Close the PRODUCT DETAILS table.

B Looking at the Forms

Two forms have been prepared for you. The CUSTOMER SUB-FORM which displays the details from the CUSTOMER DETAILS table and the INVOICE MAIN FORM which you will need to complete.

5 Open the PRODUCT DETAILS table, set the view to DESIGN VIEW and notice that PRODUCT ID has been set the a PRIMARY KEY field. It will provide data to the LINE ITEMS table via this field.

1 Open the CUSTOMER SUB-FORM form and notice that fields have been arranged in a normal address format.



2 Close the CUSTOMER SUB-FORM form.

4 Close the INVOICE MAIN FORM form.

Creating the Invoice Table

An invoice table is required to store details every time an invoice is sent. This table simply records the INVOICE NUMBER, the CUSTOMER ID and the DATE of the purchase. The links that we make to the other tables will display other details such as product name and retail price.

3 Open the INVOICE MAIN FORM form. A logo has been prepared for you. Your task will be to complete the rest of this form so that a functional invoice is created.

1 Open the CREATE tab in the RIBBON and select the TABLE DESIGN icon.

2 Enter the FIELD NAME:

Invoice No

Set is DATA TYPE to AUTONUMBER and enter the DESCRIPTION:

Provide a unique number for each invoice.



NOTE: The AUTONUMBER field type will tell the program to provide a new number every time an invoice is created so that no two invoices will ever have the same number.

NOTE: i The PRIMARY KEY will index the table so that it is listed in INVOICE NO order.

ii The format (00000) will set each number to five digits, for example, 00001, 00002, etc.

3 Click on the PRIMARY KEY button in the toolbar to set the INVOICE No field as the PRIMARY KEY field.

4 In the FIELD PROPERTIES pane set the FORMAT box to 00000.

5 Click in the second FIELD NAME cell and enter the field name:

Customer ID

6 Set DATA TYPE to TEXT, with a FIELD SIZE of 10 and a DESCRIPTION:

Identity code for each customer



Saving the Table

3 To allow for linking of tables we should enter some test data which can be deleted later.

NOTE: The AUTONUMBER command enters the INVOICE No for you and it was formatted to 5 digits.

7 In the third FIELD NAME cell enter:

Date Sold

1 Click on the SAVE icon in the QUICK ACCESS TOOLBAR.

8 Set the DATA TYPE to DATE/TIME with a FORMAT set to SHORT DATE and a DESCRIPTION:

Records the date the invoice was issued

2 Call the table:

Invoice Details

and select OK.

4 Set the screen to DATASHEET VIEW, press the tab key to set the cursor in the CUSTOMER ID field and enter the following data:

C0002 4 Oct 2008 <tab> C0003 5 Oct 2008 <tab>



5 Close the table.

Creating the Relationships

To set up the invoice system the relationships between the tables must be set. This is the most critical part of the database system.

1 Open the DATABASE TOOLS tab in the RIBBON and click on the RELATIONSHIPS icon.

2 If the SHOW TABLE dialogue box doesn’t open, click on the SHOW TABLE icon in the RIBBON.

3 In the SHOW TABLE dialogue box, double click on the CUSTOMER DETAILS table to add it to the RELATIONSHIPS window.

4 Double click on the INVOICE DETAILS table, followed by the LINE ITEMS table, followed by the PRODUCT DETAILS table to add those tables to the RELATIONSHIPS window.



NOTE: The INVOICE DETAILS table is basically the control centre of the system so we will display that table higher than the other tables.

A Relating the Customer Details and Invoice Details Tables

The CUSTOMER DETAILS table is related to the INVOICE DETAILS table as a ONE TO MANY relationship using the CUSTOMER ID fields. The ONE customer can have MANY invoices, but each invoice has only ONE customer.

5 Close the SHOW TABLE dialogue box and move the CUSTOMER DETAILS, LINE ITEMS and PRODUCT DETAILS tables down by about 2 centimetres.

1 Click on the CUSTOMER ID field in the CUSTOMER DETAILS table and drag it over the CUSTOMER ID field in the INVOICE DETAILS table.



NOTE: CASCADE DELETES would not be appropriate here. If we deleted a customer we would not want to delete any previous invoices that were sent to that customer.

2 In the EDIT RELATIONSHIPS dialogue box click on the JOIN TYPE button to display the JOIN PROPERTIES dialogue box.

4 You will be returned to the EDIT RELATIONSHIPS dialogue box. Select ENFORCE REFERENTIAL INTEGRITY. This will ensure that no customer can be placed in the invoice unless they are in the CUSTOMER DETAILS table. Click on CREATE to complete the relationship.

5 The relationship is created and the ONE TO MANY symbols should be displayed in the relationship line.

3 In this case you only want to show a customer once on each invoice when the CUSTOMER ID fields are the same so leave option 1 selected and select OK.



B Relating the Invoice Details and Line Items Tables

The INVOICE DETAILS table is related to the LINE ITEMS table as a ONE TO MANY relationship using the INVOICE NO field. The ONE invoice can have MANY line items.

NOTE: The INVOICE NO field in the INVOICE DETAILS table is the PRIMARY KEY (or PARENT) field and the INVOICE NO field in the LINE ITEMS table is the FOREIGN KEY (or CHILD) field.

1 Click on the INVOICE NO field in the INVOICE DETAILS table and drag it over the INVOICE NO field in the LINE ITEMS table to receive the second relationships dialogue box.

2 Click on the JOIN TYPE button to display the JOIN PROPERTIES dialogue box.

3 In this case we want to show all the INVOICE DETAILS records and only those LINE ITEMS records that have the same INVOICE NO. So select option 2 and click on OK.



C Relating the Line Items and Product Details Tables

The LINE ITEMS and PRODUCT DETAILS tables are linked as a ONE TO MANY relationship by the PRODUCT ID field. The ONE product can be displayed in MANY line items.

4 Turn on ENFORCE REFERENTIAL INTEGRITY. We don’t want a line item that doesn’t have an INVOICE NO the same as one of the records in the INVOICE DETAILS table.

6 Click on CREATE and the ONE TO MANY relationship should be created.

5 Turn on CASCADE DELETE RELATED RECORDS. In this case if an INVOICE was deleted (for non-payment, for example) we would want the corresponding records to be deleted from the LINE ITEMS table.

1 Drag the PRODUCT ID field (PRIMARY KEY field) in the PRODUCT DETAILS table over the PRODUCT ID field (FOREIGN KEY field) in the LINE ITEMS table.

Documents

Learning Microsoft Access 2007 - Invoices