Doing Joined Views

WHY DO JOINED VIEWS_

When you create a joined view, you can make thematic maps or add labels to maps using any of your data fields. The drop-down field lists in the theme and label dialog boxes will contain the fields from the map layer and the fields from your data file.

RULES TO REMEMBER

1. The values in one of the columns in your dataview must match the values in one of the columns of the layer. The column headings or names of the fields can be different, as long as the values match.

2. You can edit the data in a joined view, but you cannot edit the two fields that you used to create the joined view, because these fields are the glue that hold the two files together.

3. You cannot add or delete records to to the dataview, since what appears to be a single record in the joined view is really a combination of data from two different places.

4. When your data has more than one record for each map feature that is part of your join, the software computes the total number of records in your data for each map feature, and the sum, average, minimum and maximum value of each numeric field in your table. 

5. If your data includes records that don't match any of the features of the map, those records will not be part of the joined view.

6. If the map layer has features that don't have matching records in your data file, the joined view will show that the data for those features are missing.

CHARACTERISTICS OF JOINED VIEWS

1. You don't need to do anything special to save a joined view. When you save a map, layout or dataview that is based on a joined view, the software saves the joined view automatically.

2. When you open a map, dataview or layout that contains a joined view, the software recreates the link from the map layer to your data.  If the values in your data file have changed, the map or dataview will show all of those changes.

3. When your data has more than one record for each map feature that is part of your join, the software computes the total number of records in your data for each map feature, and the sum, average, minimum and maximum value of each numeric field in your table. 

FOR EXAMPLE: You are doing a join between a list of housing projects in different cities and your map's city layer. You have more than one project per city. The software will compute the number of projects per city in the resulting joined view. In addition, you have other fields in your data with more information about each of the projects, such as the level of funding. The software will give you the sum, average, minimum and maximum level of funding for the projects in each city.