[GRASS-user] Re: Cat problem with v.db.join

[Wesley Roberts]

Hi All,

I posted the question below a couple of months ago regarding the use of v.db.join. At the time I was using version 6.2.3 and even installed 6.3 but I got no luck using this tool. Markus and I then communicated several times and still I was not able to join the tables. 

I am thinking that I need some clarification on the tool use and the importance of 'cat'. In my scenario I was using the 'cat ' column as my joining field and given that both vector db's had a cat column this would not help. I then created two new columns with new and unrelated names and again the 'cat' issue arose. I guess the trick is to export your join table and remove the cat column / rename it to something else. Is this the solution? Also I don't think it is wise trying to join two vectors db files together, I am pretty sure that is where I went wrong.

Does anyone have a protocol or method to use when joining a the tables from two vectors currently residing in the same mapset?

As always, many thanks for your help
Wesley

>>> Wesley Roberts 06/25/08 3:57 PM >>>
Dear User list,

I am having some trouble with v.db.join.

I have 13 point vector files with tables connected and created using sqlite. 

I copy one of the files and rename it AnalysisData

I would now like to use v.db.join to join all of my 13 files to AnalysisData. All 13 files have the same number of points as they were generated from rasters of exactly the same size (125*125). My join field is cat in both and unfortunately I have run into the duplicate 'cat' issue mentioned in the archives. I then updated AnalysisData and generated a new column and copied the values from 'cat' using v.db.update to create a new join column. Again the 'cat' issue poped up. It isnot possible to change the column name cat either.

In the archives I see that this problem has been solved in 6.4 but am weary of installing a 'development' version of grass.

One other thing, surely all grass vectors have a column 'cat' and even if they were not used in the join the problem would persist.

Am I missing something?

Many thanks for all your help,
Wesley

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