Maptitude^® On-Line Training

Dataviews

• One-to-One: for every feature on the map, there is one record in the table; e.g., state data for each state on the map.
• Many-to-One: for a group of features on the map, there is one record in the table; e.g., joining state summary data to counties on the map.
• One-to-Many: for a feature on the map there may be more than one record in the table; e.g. customers joined to ZIP Codes. Must summarize the customers to show the data on the map.

When you join a layer and a table to create a joined view, there is often a one-to-one correspondence between the records in the layer and the records in the table. Sometimes the layer and the table do not match record for record. There are two distinct possibilities:

• The layer has several records that match a single record in the table. This is called a many-to-one joined view..
• The layer has one record that matches several records in the table. This is called a one-to-many joined view.

Usually, Maptitude can automatically tell whether the layer and the data table should be joined one-to-one or one-to-many. If you want to make sure the data are joined the way you want, use the Options tab in the Join dialog box.

For a one-to-many joined view, Maptitude creates an aggregate join. You can compute the sum, average, low and high values for the records in the table that go with each record in the layer. The result is one row for each record in the layer that aggregates the values in the fields for all of the matching records in the table. You can use these aggregated values for thematic maps, labels and other uses.