[GRASS-user] Selecting entries in a vector map

GRASS GRASS user
1

I am new to grass, but not GIS (I was trained in ArcGIS in collage a year or so ago.) I feel like what I am trying to do is simple, yet I am not having any luck.
I have two vector maps, one of zipcodes in New York State, and one of New York counties. The goal is to have a map of New York City by zipcode. I was going to select the New York City counties that are NYC (the fine folks at the NYS gis repository already have this as a category in the County file.) Unfortunately, I cannot get past the first step. Trying to use the SQL query from the “GIS Attribute Table Manager” causes GRASS to crash (I’m using windows GRASS.) Using the selection option from d.vect causes it to display nothing. I’m not certain about the proper syntax for the SQL query, but I have tried all the obvious options. the field is called NYS and is Y/N. So as far as I can tell, the SQL query should be something like NYS = Y or NYS = “Y”
Do I need to install SQL under windows to have the SQL queries work? It doesn’t look like it as far as I can tell from the documentation. am I missing something with the SQL query? Is this a known bug?

Thanks for your Help,
Christopher

2

On Fri, Oct 25, 2013 at 8:37 PM, Christopher Schroeder
<christopher@boozecarriage.com> wrote:

I am new to grass, but not GIS (I was trained in ArcGIS in collage a year or
so ago.) I feel like what I am trying to do is simple, yet I am not having
any luck.

So let's hope to improve that :slight_smile:

I have two vector maps, one of zipcodes in New York State, and one of New
York counties. The goal is to have a map of New York City by zipcode. I
was going to select the New York City counties that are NYC (the fine folks
at the NYS gis repository already have this as a category in the County
file.) Unfortunately, I cannot get past the first step. Trying to use the
SQL query from the "GIS Attribute Table Manager" causes GRASS to crash (I'm
using windows GRASS.)

Well, "this should not happen". Which version do you use exactly?
And this query?

Using the selection option from d.vect causes it to
display nothing. I'm not certain about the proper syntax for the SQL query,
but I have tried all the obvious options. the field is called NYS and is
Y/N. So as far as I can tell, the SQL query should be something like NYS =
Y or NYS = "Y"

It depends on your DB backend. Unfortunately SQL is not SQL at 100%.
Please see also
http://grass.osgeo.org/grass64/manuals/sql.html

Do I need to install SQL under windows to have the SQL queries work?

No, nothing to install.

It doesn't look like it as far as I can tell from the documentation. am I
missing something with the SQL query? Is this a known bug?

We need to know you query for this and which DB backend you use.

Best
Markus (travelling now)