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Attribute Table Imports 0 (zero) for empty data

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#1
Bob J.

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I'm looking for a best practice or method to prevent ARCmap from associating a 0 (as in zero) to a cell in the attribute table, when in fact the cell should be "empty" or "blank".

I think I mostly understand "null", "blank", "empty"...
The data I import to ARC is coming from Access.
Access is getting its tables from imports of Excel spreadsheets.

Usually, the "blanks" are true blanks in Excel..They have never contained data, but the possibility exists that they did and are now "empty".
Access doesn't seem to mind, and brings in the data. I see "empty" cells in the resulting tables, which is what I want and expect..

But upon import to ARCmap (add data as a route event) the cells that were "blank" in Access now have a 0 (zero) in place. That is undesirable an incorrect in terms of my data...

ARCmap identifies the blanks as "null". (It should identify them as something else, maybe blank, empty?..but not NULL, which ends up being represented as a 0).


Is there some check you can suggest that I can run to ensure that my resultant attribute tables will come into ARCmap with "blanks" instead of 0 ?

Edited by Bob J., 28 August 2008 - 09:41 AM.


#2
sitesatlas

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Bob,

I'm not familiar with ArcMap, but I've had a similar problem with Manifold. You might try importing those columns as text. If you need to work with the values as numbers, you could duplicate the problem columns and import one as a number and the other as text so you can select the null entries when necessary.

I'm interested to see what other users think since this is a problem I run into frequently.
Michael Borop
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#3
graveldraw

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Bob,

I'm not familiar with ArcMap, but I've had a similar problem with Manifold. You might try importing those columns as text. If you need to work with the values as numbers, you could duplicate the problem columns and import one as a number and the other as text so you can select the null entries when necessary.

I'm interested to see what other users think since this is a problem I run into frequently.



I think <Null> is the correct term in databases for "Empty" or fields with unknown values. Arcmap is correct to display these as <Null>, but I don't know how they end up as 0 or zero. Is there a default applied? Is there a table/column constraint?

Apparently, Manifold does not support Null values in numeric fields. If the data has nulls you can format as text, then use the CAST function to change datatype in sql when needed for math operations. I don't know if ArcMap has a CAST function?

Best,
Dan




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