Ask A Cartographer

Can I calculate on an alphanumerica text data type?

July 31 2008 | 0 comments
Categories: Map Data

I need to be able to calculate a field of acres but I'm afraid to make it a numeric data type because some of the rows will be populated with UNK for unknown. Which data type do I choose when setting up the feature class?

Mapping Center Answer:

Since the primary purpose of having the area is to use it when it's available, it makes more sense to use a numeric field.  Since you're dealing with area, legitimate values will always be greater than 0 (zero), so you can use specific negative numbers to denote other states of the information the area.   For instance, -99 for "Unknown", or -98 for "In Process", etc.  When using the data, you can either use a definition query to like "Area_Acres" > 0 or if you're just displaying the data, you can set the No Data clause to be the inverse: "Area_Acres <= 0.


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