Ask A Cartographer

JOIN tables

November 17 2010 | 0 comments
Categories: Map Data

I have a non-spatial data file (Excel Spreadsheet) having multiple attributes which needs to be joined to a shape file having only one feature class (sub-district) per district. For explanation purposes, many churches or organizations working in the same sub-district of a district. I have to create a thematic map showing by name, WHICH churches or organizations are working in a particular sub-district. How can I represent this on my map? I have exhaustively researched on how to do this, yet I cannot find a way to do it without programming. If there is no possibility for a One-to-Many Join, what is the use of keeping a database? Please help.

Mapping Center Answer:

In your case, you would need a Relate (which supports one-to-one, one-to-many, and many-to-many relationships) instead of a Join. With a Relate, the associated data isn't appended to the layer's attribute table like it is with a Join, but you can still access the related data when you work with the layer's attributes.

For example, if you select a building, you can find all the tenants that occupy that building. Similarly, if you select a tenant, you can find what building it resides in (or several buildings, in the case of a chain of stores in multiple shopping centers—this is a many-to-many relationship). However, if you performed a Join on such data, ArcMap would only find the first tenant belonging to each building, ignoring additional tenants.

Once you define a Relate, you can access the related records from either table participating in the relationship. You can also identify a feature on your map using the Identify button.

In the event that you are creating Web maps, you can use ArcGIS Javascript API’s samples to show related records.

If you would like to post a comment, please login.

Contact Us | Legal | Privacy |