NAME
d.vect.pg - Display select vectors from an existing vector
map. (GRASS-RDBMS Interface Display Program)
SYNOPSIS
d.vect.pg
d.vect.pg help
d.vect.pg [-fe] key=name tab=name
[where=name] map=name [color=name]
ALTERNATE
d.vect.pg -s help
d.vect.pg [-sfe] sql=filename map=name
[color=name]
DESCRIPTION
d.vect.pg displays select vectors from an existing vector map based
on the unique values in a database column. Each row returned by a user
constructed database query will be associated with a vector feature which
is subsequently drawn on the graphics display in the active frame. The
user can control the color of the vector draw by specifying a color on
the command line.
COMMAND LINE OPTIONS
Flag:
-
-f
-
Fill polygons selected on the query criteria
-
-e
-
Extract vector objects to new map
Parameters:
-
key=databasecolumnname
-
Column in table "tab" of the currently selected database containing values
corresponding to the vector maps category values. Table is designated on
the command line by tab=tablename and vector is designated on the command
line by map=mapname.
-
tab=databasetablename
-
Table in the currently selected database containing a column which has
values corresponding to vector category values in the map designated by
map=map.
-
where=SQLwhereclause
-
SQL "where" clause which specifies the query criteria to be used in subsetting
the database. The field names specified in the where option must indicate
the column(s) to be used, the operators to be used in the evaluation and
the values which the data in the column will be evaluated against.
If the database column used as the selection criteria is a character field
then the associated value must be placed in quotes. To determine the data
types associated with columns in the currently selected database use the
g.column.pg
command with the -v flag.
Queries which are more complex are best implemented using the -s
flag and a prepared SQL file.
-
map=map
-
Name of an existing vector map with category values which correspond to
values in a specified column in the currently selected database.
-
color=name
-
Color to draw vectors in
-
Colors: red, orange, yellow, green, blue, indigo, violet, magenta, brown,
gray, white, black
ALTERNATE COMMAND LINE USAGE
The alternate command line usage is provided to simplify the process of
retrieving information from more than one table in the query criteria.
The alternate command line structure is selected using the the [-s]
flag on the command line. When using this flag the user must include the
name of a text file on the command line as well. This file must include
a complete, well formed SQL SELECT statement specifying the query criteria
to retrieve values which correspond to category values in a GRASS data
layer.
Flag:
-
-s
-
SQL select statements are input from a prepared file
-
-f
-
Fill polygons selected on the query criteria
-
-e
-
Extract vector objects to new map
Parameters:
-
sql=filename
-
SQL statements specifying well formed selection criteria.
-
map=name
-
Name of an existing vector map
-
color=name
-
Color to draw vectors in
-
Colors: red, orange, yellow, green, blue, indigo, violet, magenta, brown,
gray, white, black
EXAMPLE:
1. d.vect.pg -f key=rec_id map=kuruma_id tab=info_kuruma where='type_id
>32 and type_id < 38' color=red
Result: only polygons with type in 33-37 range would be displayed
in red color..
2. d.vect.pg -f -e -s sql=oak.sql map=kuruma_id
oak.sql is:
select rec_id from info_kuruma where type_id > 32 and type_id <38;
Result: this would be the same as in the first example, saving
extracted fetures to a new vector map.
BUGS
none
NOTE
This program requires the Postgres database software.
v.extract is loaded from within d.vect.pg if '-e' flag
was given.
SEE ALSO
g.column.pg, g.select.pg,
g.stats.pg,
g.table.pg,
d.rast.pg,
d.site.pg,
d.what.r.pg,
d.what.s.pg,
d.what.v.pg,
v.reclass.pg
AUTHOR
Original Informix SQL-tools: James A. Farley, Wang Song, and W. Fredrick
Limp University of Arkansas, CAST
Postgres modifications: Janne Soimasuo, Faculty of Forestry, University
of Joensuu, Finland.
Updated to GRASS 5 by Alex Shevlakov (sixote@yahoo.com)