[GRASSLIST:1395] Re: problems connecting to database via odbc & v.reclass.pg problems

[Markus Neteler]

On Tue, Jan 23, 2001 at 04:05:35PM +0100, mlennert at club.worldonline.be wrote:
> 
> > > As to the postgres modules, they are great, but there still seems to be an 
> > > inconsisteny in the v.reclass.pg html-page. In the text, sql queries are 
> > > mentioned, but in the "synopsis" section the keyword is 'pql'. Then in the 
> > > description of the keywords, no mention of pql, but of sql. In the example, 
> > > the same problem again:
> > > 
> > > "v.reclass.pg sql=vect.sql key=tlid input=t.roads.pg out­put=t.roads.12 
> > > 
> > > vect.pql: retrieve unique (t.tlid,t.cfcc) from t in type1
> > > where cfcc ~ "A1"
> > > sort by tlid"
> > > 
> > > So, if someone could explain, what I should use, sql or pql...
> > Thanks for identifying the inconsistency. I have updated the html
> > page to "sql" and "postQUEL" to "SQL". See here:
> > http://www.geog.uni-hannover.de/grass/gdp/html_grass5/database.html
> > 
> > > Also, I do not find the explanation of the 'where' parameter very clear.
> > > How should this be formulated exactly ? And if I understand correctly, I
> > > can only extract one set of data if I use this option, i.e. I can only
> > > create one category.
> > 
> > Please remind that the *.pg pages might need final updating (web page:
> > "(note: needs to be updated)"). If you encounter other problems or have text
> > pieces to improve the pages, please let me know.
> 
> Thanks for doing the update, but is the "retrieve" statement you use in the 
> example a valid SQL command ? I can't find it in the postgresql commands. 
> Should'nt it be "select" ?
Moritz,

please try if "select" is o.k. (as it sounds reasonable). Then I will
update this as well (sorry, no time to test myself).
 
> Secondly, I think an example for the other way of using v.reclass.pg, i.e. 
> without an external sql file would be very helpful.
Yes, I agree.
Please see
http://www.geog.uni-hannover.de/grass/sqlgrasslist.html
 -> Small raw tutorial: first-steps for usage of PostgreSQL/GRASS interface 

This is very incomplete but such an example is there. If you could 
write a small piece of text for the html-page, I'll add this.
Thanks for your cooperation!
 
> > > I find the odbc reclass much easier to use, but this might just be my lack of 
> > > understanding of v.reclass.pg
> > > 
> > > More generally, I like the idea of having one interface (odbc) which I can
> > > use in several programs, such as Grass, R, etc...
> > Yes, that's the intention of Radim's db.* modules...
> 
> Yes, and I want to thank him again for those...if only I could get them to
> work here ;-)
> 
> I also read the paper that Roger and you (Markus) wrote on R, Grass, and
> Postgres and I do believe that this is an important issue, as it touches
> user friendliness in terms of data handling...
Yes, here much more has to be done. I hope the best for GRASS 5.1 :-)

 Markus Neteler