[GRASS-user] How to JOIN a table to vector layer using MySQL

[Nicolas Devaux]

Raffaele Morelli a écrit :
> Hi
> I use to work with grass vectors with attributes stored in a MySQL db.
> But it's not very clear when you say
>
>
>     I did the Join operation with Mysql and it works perfectly. But,
>     when I
>     come back in Grass, it is not possible to see the result within the
>     attribute table... Joined attributes are not in the table. It
>     seems that
>     grass is not able to see results of the joined operation made in
>     Mysql.
>
>
> What kind of join are you talking about?
> Do you mean a db view resulting from a two (or more) table join?
>
> Vectors have categories which identify polygons. You must "link" those 
> values with the corresponding key on your table, so when calling 
> db.connect you must specify a valid database name, valid table name 
> and finally a valid key on your table.
> Valid means that polygons id's (categories) need a value stored in the 
> table to link to.
>
> Try to create a dummy table containing a field with the same value 
> your categories have, and link it to the vector using that field.
>
> Hope this helps
>
Thanks for this answer, but it did not really help me.
I know what is a table join, and as I say, I made the join (using Cat as 
common fields of both tables to join), but what I want is to see result 
within Grass on the attribute table of my vector layer.

Exemple : I have a GPS points vector layer call GPS which locate houses. 
Attributes table contain only categories number. I use MySql to import 
another table containing points informations (point id and house's owner 
names). I make the table join within Mysql and it works (I have in the 
attribute table of GPS points cover the name of house's owners. Now, I 
want to be able to use this information within Grass, and when I look at 
the attribute table, I don't have owner names, I have only cat number as 
in the attributre table before the join operation made in MySql. I think 
that I miss something... I would like to transform the join operation 
results as permanent information within my points cover attribute table....
Perhaps I should make the join table operation directly in Grass instead 
of doing it in MySql ? If is is the solution, how can I do, what is the 
command ?

I hope this is more clear...

Thanks