ACC2: How to Determine a Percentage from a Column of Values

MORE INFORMATION

To calculate a percentage for each unique record in a column of information, follow these steps.

CAUTION: Following the steps in this example will modify the sample database NWIND.MDB. Before testing the following example, you may want to back up the NWIND.MDB file, or perform these steps on a copy of the NWIND database.

1. To determine the total count of the orders shipped by each shipper, create the following totals query, and add the Orders table:
   

         Query Name: ShipperCounts
         -------------------------------
         Type: Select Query
   
         Field: [Ship Via]
            Table: Orders
            Total: Group By
            Sort: Ascending
         Field: ShipperCount: [Ship Via]
            Table: Orders
            Total: Count
   						

   
   NOTE: To turn on the Totals feature in a query, click Totals on the View menu.
2. To determine the total count of all the orders shipped, create the following totals query, and add the Orders table:
   

         Query: ShipperTotalCount
         ----------------------------
         Type: Select Query
   
         Field: TotalCount: [Ship Via]
            Table: Orders
            Total: Count
   						

3. To produce the percentages from the previous two queries, create the following query, and add the ShipperCounts and the ShipperTotalCount queries:
   

         Query: ShipperPercentage
         ------------------------
         Type: Select Query
         Join: None
   
         Field: [Ship Via]
            Table: ShipperCounts
         Field: [Company Name]
            Table: Shippers
         Field: ShipperPercent: Format([ShipperCount]/[TotalCount],"Percent")
   						

Running the Queries

Because there is no join between the two queries used in the third query, the third query creates a Cartesian product between the ShipperCounts and ShipperTotalCount queries. But, because the ShipperTotalCount query has only one value, the result query has only as many records as the ShipperCounts query, and the expression is evaluated for each record to obtain the desired results.

When you run the ShipperPercentage query, the following results are produced:

Ship Via   Company Name       ShipperPercent
--------------------------------------------
       1   Speedy Express     29.68%
       2   United Package     39.42%
       3   Federal Shipping   30.89%