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<title>GRASS GIS: v.db.connect</title>
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<h2>NAME</h2>
<em><b>v.db.connect</b></em> - Prints/sets DB connection for a vector map to attribute table.
<h2>KEYWORDS</h2>
vector, database, attribute table
<h2>SYNOPSIS</h2>
<b>v.db.connect</b><br>
<b>v.db.connect help</b><br>
<b>v.db.connect</b> [-<b>pgcod</b>] <b>map</b>=<em>name</em> [<b>driver</b>=<em>name</em>] [<b>database</b>=<em>name</em>] [<b>table</b>=<em>name</em>] [<b>key</b>=<em>name</em>] [<b>layer</b>=<em>integer</em>] [--<b>verbose</b>] [--<b>quiet</b>]
<h3>Flags:</h3>
<DL>
<DT><b>-p</b></DT>
<DD>Print all map connection parameters and exit</DD>
<DT><b>-g</b></DT>
<DD>Print all map connection parameters and exit in shell script style</DD>
<DD>Format: layer[/layer name] table key database driver</DD>
<DT><b>-c</b></DT>
<DD>Print types/names of table columns for specified layer and exit</DD>
<DT><b>-o</b></DT>
<DD>Overwrite connection parameter for certain layer</DD>
<DT><b>-d</b></DT>
<DD>Delete connection for certain layer (not the table)</DD>
<DT><b>--verbose</b></DT>
<DD>Verbose module output</DD>
<DT><b>--quiet</b></DT>
<DD>Quiet module output</DD>
</DL>
<h3>Parameters:</h3>
<DL>
<DT><b>map</b>=<em>name</em></DT>
<DD>Name of input vector map</DD>
<DT><b>driver</b>=<em>name</em></DT>
<DD>Driver name</DD>
<DD>Options: <em>odbc,dbf,pg,sqlite,mesql,mysql,ogr</em></DD>
<DD>Default: <em>dbf</em></DD>
<DT><b>database</b>=<em>name</em></DT>
<DD>Database name</DD>
<DD>Default: <em>$GISDBASE/$LOCATION_NAME/$MAPSET/dbf/</em></DD>
<DT><b>table</b>=<em>name</em></DT>
<DD>Table name</DD>
<DT><b>key</b>=<em>name</em></DT>
<DD>Key column name</DD>
<DD>Must refer to an integer column</DD>
<DD>Default: <em>cat</em></DD>
<DT><b>layer</b>=<em>integer</em></DT>
<DD>Layer number</DD>
<DD>A single vector map can be connected to multiple database tables. This number determines which table to use.</DD>
<DD>Default: <em>1</em></DD>
</DL>
<h2>DESCRIPTION</h2>
<em>v.db.connect</em> prints or sets database connection for a vector
map. The user can add or remove link to attribute table on the certain
layer.
<h2>NOTE</h2>
If parameters for database connection are already set with
<a HREF="db.connect.html">db.connect</a>, they are taken as default values and
do not need to be spcified each time.
<p>
When printing database connection (<em>p</em> or <em>g</em> flag) the parameter
<em>layer</em> is ignored, i.e. <b>all</b> connections are printed to the
output.
<p>
<b>Attention:</b> Removing a vector map will also delete all tables
linked to it! If you use <a HREF="db.connect.html">v.db.connect </a>to
link further tables to your map, it is advisable to make a copy from
those tables first and connect the copied tables to the vector map
(see also <a HREF="v.overlay.html">v.overlay</a>).
<h2>EXAMPLE</h2>
<h3>Print database connection</h3>
Print all database connection parameters for vector map.
<div class="code"><pre>
v.db.connect -p map=roads
</pre></div>
<p>
Print column types and names of table linked to vector map.
<div class="code"><pre>
v.db.connect -c map=roads
</pre></div>
<h3>Connect vector map to database (DBF driver)</h3>
Connect vector map to DBF table without or with variables.<br>
<p>
Using default DB connection:
<div class="code"><pre>
v.db.connect map=vectormap table=table
</pre></div>
<p>
Using hardcoded path to DBF directory (not recommended):<br>
<div class="code"><pre>
v.db.connect map=vectormap table=table database=/home/user/grassdata/spearfish60/PERMANENT/dbf
</pre></div>
<p>
Using variable as DBF directory definition, single quotes must be used:<br>
<div class="code"><pre>
v.db.connect map=vectormap table=table database='$GISDBASE/$LOCATION_NAME/$MAPSET/dbf/'
</pre></div>
<p>
Connect vector map layer 2 and key ID to database with variables (note: if needed, single quotes must be used for the <em>database</em> parameter):
<div class="code"><pre>
v.db.connect map=vectormap table=table layer=2 key=ID
</pre></div>
<h3>Connect vector map to database (MySQL driver)</h3>
<div class="code"><pre>
# note: connection which requires password
db.connect driver=mysql database="host=dbserver.foo.org,dbname=my_database"
db.login user=joshua [password=xxx]
# ... or enter password interactively.
db.tables -p
# connect external table to layer 2:
v.db.connect map=my_map table=my_mysql_table key=baz layer=2
v.db.connect -p my_map
</pre></div>
<h3>Connect vector map to database (PostgreSQL driver)</h3>
<div class="code"><pre>
# note: connection without password being asked
v.db.connect map=vectormap table=table layer=1 key=oid driver=pg \
database="host=myserver.itc.it,dbname=mydb,user=name" \
table=mytable key=id
</pre></div>
<H3>Store geometry in GRASS but attributes in PostgreSQL</H3>
This example illustrated a mixed data storage with possibility
top update attributes in external PostgreSQL database:
<div class="code"><pre>
# Check current settings for attribute storage:
db.connect -p
# Import table from PostgreSQL to new map
# (NOTE: output map name needs to be different from table name in
# case that GRASS is connected to PostgreSQL):
v.in.db driver=pg database="host=localhost,dbname=meteo" \
table=mytable x=lon y=lat key=cat out=mytable
v.db.connect map=mytable -p
# Cancel table connection between map and attribute table:
v.db.connect map=mytable -d
v.db.connect map=mytable -p
# Drop table which was replicated due to import:
db.tables -p
echo "DROP TABLE mytable" | db.execute
db.tables -p
# reconnect map to table in PostgreSQL:
v.db.connect map=mytable driver=pg database="host=localhost,dbname=meteo" \
table=mytable key=cat
# Now the geometry is stored in GRASS while the attributes are stored
# in PostgreSQL.
</pre></div>
An alternative is to create a "view" of only ID, x, y [,z] columns and
to use <a HREF="v.in.db.html">v.in.db</a> on this view, then connect the original
table to the geometry. This will be faster if the original table
is very large.
<H3>Store geometry in GRASS but attributes in PostGIS</H3>
This example illustrated a mixed data storage with possibility
top update attributes in external PostGIS database:
<div class="code"><pre>
# Check current settings for attribute storage:
db.connect -p
# Import table from PostGIS to new map
# (NOTE: output map name needs to be different from table name in
# case that GRASS is connected to PostGIS):
v.in.db driver=pg database="host=localhost,dbname=meteo" \
table=mytable x="x(geom)" y="y(geom)" key=cat out=mytable
v.db.connect map=mytable -p
# Cancel table connection between map and attribute table:
v.db.connect map=mytable -d
v.db.connect map=mytable -p
# Drop table which was replicated due to import:
db.tables -p
echo "DROP TABLE mytable" | db.execute
db.tables -p
# reconnect map to table in PostGIS:
v.db.connect map=mytable driver=pg database="host=localhost,dbname=meteo" \
table=mytable key=cat
# Now the geometry is stored in GRASS while the attributes are stored
# in PostGIS.
</pre></div>
<h2>SEE ALSO</h2>
<a HREF="db.connect.html">db.connect</a>,
<a HREF="db.copy.html">db.copy</a>,
<a HREF="db.tables.html">db.tables</a>,
<a HREF="v.db.addtable.html">v.db.addtable</a>,
<a HREF="v.db.droptable.html">v.db.droptable</a>,
<a HREF="v.db.addcol.html">v.db.addcol</a>,
<a HREF="v.db.dropcol.html">v.db.dropcol</a>,
<a HREF="v.external.html">v.external</a>,
<a HREF="v.in.db.html">v.in.db</a>,
<a HREF="v.overlay.html">v.overlay</a>
<h2>AUTHOR</h2>
Radim Blazek, ITC-Irst, Trento, Italy
<p><i>Last changed: $Date: 2007-09-10 08:58:58 +0200 (Mon, 10 Sep 2007) $</i>
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