TOP N RECORDS IN QUERY ~ LEARN MS-ACCESS TIPS AND TRICKS

Introduction.

We have seen the usage of different types of complicated Queries like the following:

Today we will learn how to define and extract the top 100 or whatever number of records or a certain percentage of the total records based on the values, in a particular Column.

Review of Rules of Queries.

You need to know only a few rules to work with this type of Query.

You may select several Columns of data from the source for output.
You must sort one or more columns of data in Ascending/Descending Order and the leftmost sorted column will pick the top valuation records.
If the output values have duplicates (duplicate values in all columns in two or more records) then you can set the Unique Values Property to Yes (a DISTINCT clause in the SELECT statement) to suppress duplicate records.
If the query has more than one Table/Query as the source and when duplicate records are found in the output; set the Unique Records Property to Yes (DISTINCTROW clause in the SELECT statement) to suppress duplicate records.

Create a Sample Query.

Open a new database or one of your existing databases.
Import the Order Details and Products Table from Northwind.mdb sample Database. The Products table is not directly used, but there is a lookup reference to this table in the Order Details table for Product Name.
Open a new Query in SQL View (without selecting a Table/Query from the displayed list).

Copy and paste the following SQL String into the SQL editing window and save the Query with the name Order_DetailsQ.

SELECT TOP 100 [Order Details].ProductID, [Order Details].UnitPrice
FROM [Order Details]
WHERE ((([Order Details].OrderID) Between 10248 And 10300))
ORDER BY [Order Details].UnitPrice DESC;

Open the Query in Design View and check the order of placement of fields and the Sort Field.
Right-click on an empty area above the column grid to display the Query Shortcut Menu and select the Properties… option to display the Property Sheet. Check the image below:
Check the Top Values Property, that set to the value 100, which dictates the Query to select 100 records with the highest Unit Price values.
Change the View of the Query into Datasheet View to display the output records. See the image given below:

The Order Details Table has several records of the same Product under different OrderIDs. We have purposely not included the OrderID field in the data column except in the criteria to select the records of OrderIDs between 10248 and 102300 and to pick some duplicate records. As you can see in the image given above; there are several duplicate records of the same product in the output. With the duplicate records, we can try out the Unique Values property settings.
Eliminating Duplicate Records.
Change the Top Values property value to All and change the Query into Datasheet View. The output will be about 150 records for OrderIDs between 10248 and 102300.
Change the Query in Design View and display its Property Sheet.
Set the Top Values property with 100 and Unique Values property to Yes.
Change the Query in Datasheet View and inspect the output.
Now the duplicate records are suppressed (29 of them) and the output is now only 71 records. The next property Unique Records can be set to Yes to get the same result when data fields are placed from two or more Tables or Queries joined together in the Query design and duplicate records are found in the output; due to a one-to-many relationship.
We have specified 100 records in the Top Values Property but the Unique Values property setting reduced the number of records to 71 after suppressing duplicates.
Change the Top Values Property setting from 100 to 25% and change the View into Datasheet View.

The percentage setting gives only one-fourth (18 records) of a Total of 71 records as output with the Unique Values setting to Yes or 39 records (one-fourth of about 150 records) with the Unique Values setting to No.

The Top Values Property sets can be a specific number or a percentage of Total Records.