[GRASS-user] Strategy For DBMS Use

[Pablo Carreira]

I have very nice results with sqlite+GRASS.

First, use an sqlite administrator software to make things easier.

 
>    1) My initial impression is that I need a separate database for each layer
> (i.e., one for highways, a separate one for streams & rivers, etc.). Is this
> correct?

One database for each LOCATION, one table for each vector.

One way of working is that You can put rivers, highways, power lines, etc. in the same "layer" and put a column in the table that describe what kind of object it is. You can play with CAT number too, like rivers is cat number x and highways is cat number y.
Then for example:
Displaying the vector you say: x=blue y=black.
In the sql you say: SELECT * FROM table WHERE description="river"


Try no to think as the obsolete shapefile style gis.


>    2) Do I manually create the databases and specify table schema within each
> location's dbf/ directory?

Just create the table and connect the LOCATION to it. "db.connect".
Any new vector or command tha creates a vector, creates also a new table in the sql database.


>    3) If I want to write SELECT statments that JOIN tables in different
> layers, then I need to open one database and attach the others. Is this done
> within GRASS?

I have never tried joining tables in different databases.

>    I'm sure that I'll have more questions as I learn how to use SQLite with
> vector attributes. The soils data in particular, has a couple of dozen
> tables associated with it.

I am a agronomist engineer an I have made soil maps and soil use maps with grass, just ask if you have more questions.


Pablo Torres Carreira
Brazil.



 		 	   		  
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