Creating a Nearest Link

Creating a nearest link from one schema to another will allow you to find out which point in a schema is closest to a point in a second schema (in a straight line). For example, you could find out which competitors are the nearest to all your stores.

In this example we will create a nearest link to find which store is the nearest to each customer.

Setting up the link:

• Go to Tools | Configure Catalog

• Double click on the Schema Group (here User Data) that holds your first schema (here Branch customers)

• Double click on the schema itself (e.g. Branch Customers)

• Highlight Superior Links and select the New... button

• Click on the down arrow next to Inferior Schema and select the schema you want to find the nearest from (eg. Branches)

• Type in a Link Name and a Link Description

Note: A link name cannot contain spaces or non-alphanumeric characters

• Change the Link Type to Exact_Within and the Link Method to Subquery

• Click on the Inf.. button

• In the Expression box, type Nearest(

• Double click on the Master table (the red table icon with a small purple key)

• Double click on the Location/Point column

• Add a comma to the end of the expression so far

• Select OK

• Click on Sup..

• Double click on the Master table and again, double click on the Location/Point column

• Add ) to the end

• Select OK

The expression should look like this:

Nearest(MASTER.POSTCODE_POINT, :MASTER.POSTCODE_POINT)

• Click Apply

• Add new record? Pick Yes then close the window

Using the link:

• Open a browse on the schema that you created the link for, here Branch Customers

• Right click and select Add Column…

• You will see the link that you just created, (here Nearest Branch), double click on it

Note: If you don’t see it you may have to go through blue link called User Data first

• Double click on the master table and select the Branch Name

• Click on the > button to move it to Selected Expressions

• Select OK

This will have added a new column to your browse listing the name of the nearest location. If you want to find the distance to this point, you will need to use a Distance expression which is covered in the tip ‘Distance between two points’.