[GRASSLIST:10293] Re: joining attribute tables using SQL commands

[wqual]

Hi Jessi,
unfortunately, it is not possible to join tables with the dbf-driver. However, 
if you use sqlite, Postgres or Mysql it's possible. There is an example for 
sqlite on this list:

--> http://article.gmane.org/gmane.comp.gis.grass.user/10882/match=sqlite+join

Best regards,

Wolfgang

--

Am Montag 13 Februar 2006 pH:11:21 nachmittags/abends schrieb j b:
> hello.
> I am a beginner trying to join attribute tables.
>
> To be more specific, I have a .dbf table called streetcl, which gives
> street blocks and their various attributes. It contains an attribute called
> FNODE_, which is the ID of its starting intersection. I used the command:
>
> echo "ALTER TABLE streetcl ADD COLUMN ELEVFROM double" | db.execute
>
> to create an attribute called ELEVFROM. In this column, i want to put the
> elevation of the intersection where each block originates. I have another
> .dbf table called intersect which gives the city's intersections; it has a
> column called ELEV (the intersection's elevation) and a column called
> STREETCL_ (the ID of the
> intersection as referred to in the streetcl table.)
>
> This seems like it should not be so complicated, but i'm getting SQL parser
> errors.
>
> My first attempt was this command:
>
> echo "UPDATE streetcl SET ELEVFROM=(SELECT ELEV FROM intersect WHERE
> intersect.STREETCL_=streetcl.FNODE_)" | db.execute
>
> This tells me:
> DBMI-DBF driver error:
> SQL parser error in statement:
> ...
>
> Then, to test, I tried to do more simple commands. I created a column in
> streetcl called TEST, and tried to set it equal to another column (same
> type)
> in streetcl, called LENGTH.
>
> echo "UPDATE streetcl SET TEST=LENGTH" | db.execute
>
> this gives me the same error. A command like:
>
> echo "UPDATE streetcl SET TEST=30" | db.execute
>
> is fine, but even:
> echo "UPDATE streetcl SET TEST=30+2" | db.execute
> (with or w/out parens around "30+2) gives me the same SQL parser error.
>
> Any idea what is going on? Am i even going about this in the right way?
> Should i be using SQL commands or is there another approach entirely?
> thanks very much.
> jessi