Step 1: Create a totals query to show the total cost price and total sale price of the wine for each supplier.

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1 Hands-On-2: Queries In D1 you used Select queries to extract required information from your database. You used these to list data that met certain criteria and also used totals queries (a special type of select query) to summarise data. In this exercise you will: Learn more about using expressions in totals queries. Create and run Action queries which allow you to make changes to your data Summarise data using Crosstab queries. 1. Using Expressions in Totals Queries Create a query to show the total profit made on wine sales from each supplier (assuming one bottle of each wine). To do this you need to use a totals query that groups the products by supplier and uses the SUM aggregate function to calculate the total cost price and total sale price of the products for each supplier. You then need to add a calculated field to the query which subtracts the total cost price from the total sale price to show the overall profit. Step 1: Create a totals query to show the total cost price and total sale price of the wine for each supplier. You should already know how to do this based on what you learned in D1. Hints: Group by supplier and sort alphabetically by Company name. The total cost price is the SUM of the CostPrice field The total sale price is the SUM of the MktValPerBottle field. Use labels for the total cost price and total sale price fields in the query grid. Use the field properties to set the format to currency. You should get the following output when you run this query: Fig 2.1 Totals query showing total cost and sale price of wine from each supplier. Step 2: Calculate profit made on wine from each supplier To create a calculated field in a query you need to put the calculation in the Field row of the query grid. (This was covered in D1, HO 10). In addition, when you are creating a calculated field in a Totals query you need to set the Total row for this type of field to Expression. Fig. 2.2 shows the field you will need to add to the query you created in Step 1 to calculate the profit. ho-020.doc 1 01/12/ :04:00

2 Note that the field names used in the expression are the labels that you gave to each of the SUMmed fields in the query you created in Step 1. Use the labels from the aggregate function fields in your expression Set Total row to Expression Fig. 2.2: Using an expression to calculate the profit in the totals query. Step 3: Calculate overall profit and increase in profit if sale price is increased by 10%. To do this you need to create three additional calculated fields. 1. A field to calculate the Total Sale Price with a 10% increase. 2. A field to calculate the profit if products are sold at these increased prices. (This will be a similar expression to the one you used to calculate the profit in Step 2 but it will use the increased sale price field.) 3. A field to calculate the difference between the original profit and increased profit. You need to work out the expressions you will need to use for each of these calculations. Don t forget to set the Total row to Expression for each of these fields. The final query output is shown in Fig Fig. 2.3 Final query output Xtra Challenge: How could you create a query that would allow the user to specify the percentage increase in sale price and then calculate the profit based on that increase? Hint: This needs to be a parameter query. ho-020.doc 2 01/12/ :04:00

3 2. Action Queries Action queries allow you to delete, update and append records in existing tables and make new tables. WARNING: Unlike Select queries which simply select and show data these queries CHANGE data. Once the data is changed you cannot reverse the changes. Therefore while you are practising with these queries ensure that you always have a backup copy of the original data. Before you run an action query you can check that it is selecting the intended records by using the view button to change to datasheet view. Once you are happy with the result you can run it using the run button. 2.1 Use Make Table Queries to create Look-up tables In D1 you learned to create combo and list boxes in forms based on look-up tables. It is often better to use a look-up table rather than a value list for these controls as tables are easier to update when new values need to be added. You will need look-up tables for the Colour and Type fields in the Products table for the form you create in Hands-on 5. These tables will consist of a list of values that could be entered into these fields. You can easily make the colour look-up table by simply creating a table and typing in the values. (There are currently only Red and White wines in the products list but you might also want to include Rose.) This is not such a good approach for the Type look-up table as there are many different values in this field. By using a Make Table Query you can easily create a table that lists all these values. Any other values can easily be added to the table later if required. Step 1: Create a query to list each wine type from the products table Create a new query based on the Products table Add the Type field to the query grid. Run the query. You will see a list of the Types for each of the wines in the database. As there may be more than one wine of each type, many of the values appear more than once which is clearly not what is required for a look-up table. Query Properties button Modify the query to display each value once only. To do this you need to display the query properties (click the toolbar button or right click in the top section of the query grid) and set the Unique Values property to Yes. Once you have done this, run the query again to check the results. Each value from the type field should appear just once in the list. Unique Values Property ho-020.doc 3 01/12/ :04:00

4 List of types from products table. Step 2: Change the query type to Make Table To make this list into a new table you need to change the query type to make table. Click the Query Menu to display the list of query types and select Make Table. The Make Table dialog box opens. Type the name of the table you want to create (tblwinetypeslookup) and click OK. Note: You have not created the table at this point, you have simply set up the query so that it will create the table when it is run. Run the query to create the table. Note: To run an Action Query you need to use the Run button (red exclamation mark) on the toolbar. The View button (on left end of toolbar) simply shows which records the query will affect. You will get a message informing you that you are about to paste 11 rows into a new table. Click OK to create the table. The table you have just created will now be in the table list in your database. Open it to check that it has been created as you intended. Step 3: Attach the look-up table to the Type field in the Products table Open the Products table in design view and select Look-up as the data type for the Type field. Follow the instructions in the Wizard to create the look-up field. Change to table view to see what effect this change has had. Change back to Design view and click the Look-up tab in the field's properties to see the settings that the Wizard has made. (Notice that the property list is almost identical to the properties for the combo boxes you have created in forms.) You will see that the Wizard has created an SQL SELECT statement as the row source. Click the arrow to the right of the row source to display a list of the tables in your database. Select the type look-up table from this list to replace the SELECT statement created by the Wizard. Check the table again Make any other look-up tables you require (e.g.colour, Country) in a similar way. ho-020.doc 4 01/12/ :04:00

5 2.2 Practise creating and running Action Queries Use the reference to revise the types of Action Query: Reference: Action Queries Section 3.1 You will now create and run some action queries. Save each query with a suitable name so that you can use it again. Use the table you make in step 1 as the basis for all the other action queries NOT the original Bacchus database tables. 1. Use a make table query based on the products table to create a table listing all the details for dry red wine. Open the table to check that it has been created successfully. (Note that any field properties are not transferred.) 2. Use an append query to add details of sweet wine to this table. Again check that the fields have been added to the table as expected. 3. Use a delete query to remove records for white wine from the above table. 4. Use an update query to increase the market value for the wines in this table by 10%. Check that this has worked correctly by comparing the values in this table with those in the original products table. 3. Crosstab Queries Crosstab queries allow you to summarise data in your database. Reference: Crosstab Queries Section 3.4 Using the example below as a guide and by following the instructions underneath you are now going to create a new crosstab query using the Crosstab wizard. (This crosstab query is based on tblproducts table) ho-020.doc 5 01/12/ :04:00

6 5. In the Database window, click the Queries tab, and then click New. 6. In the New Query dialog box, click Crosstab Query Wizard. 7. Click OK. 8. Follow the directions in the wizard dialog boxes. In the last dialog box, you can choose to run the query or see the query's structure in Design view. If the resulting query isn't exactly what you want, you can rerun the wizard or change the query in Design view. 9. Save the query as qrycolourcountrycrosstab Use the example above to familiarise yourself with the way in which crosstab queries are constructed. Note the extra rows in the query grid - total and crosstab. These are automatically displayed when Crosstab is selected from the Query menu. In the Crosstab row you can only have one Column Heading and one Value field but you can have multiple Row Heading fields. Once you are happy with the way crosstab queries work, try the exercises below. You can use the Wizard or try creating them yourself in Design view. Additional crosstab queries 1. Create a crosstab query to show a count of the number of customers of each membership type together with the number living in each area (as recorded in the Address2 field). The result should appear as in the screenshot below: Add criteria to this query so that it only displays counts for members living in London. The Crosstab Wizard does not allow you to add criteria. If you want to use criteria with a query created by the wizard you have to add the criteria in design view. 2. Create a crosstab query to show supplier names, a count of the wines of each colour and the total number of products supplied. Your result should look like the screenshot below: ho-020.doc 6 01/12/ :04:00

7 The crosstab wizard only lets you select from one table or query but you need to use data from two tables for this query. To do this you can either create a select query to combine the fields you need from the two tables and then select this query with the wizard or you can create the crosstab query manually in design view using both tables. Stop and Reflect What is the difference between using a value list and a table as the row source for a combo or list box? How can you decide which is most appropriate? What is the main advantage with using a look-up table? Why is it important to back-up data before using an action query? How can you view the results of an action query without running it? When might you want to base a query on another query rather than on a table? When are the Zoom Box and Expression Builder useful? How can you display them? What is the difference between a row heading and a column heading in a crosstab query? Can you have more than one row heading? Can you have more than one column heading? ho-020.doc 7 01/12/ :04:00