.TH v.db.connect 1grass "" "GRASS 8.3.2" "GRASS GIS User's Manual"
.SH NAME
\fI\fBv.db.connect\fR\fR  \- Prints/sets DB connection for a vector map to attribute table.
.SH KEYWORDS
vector, attribute table, database, layer
.SH SYNOPSIS
\fBv.db.connect\fR
.br
\fBv.db.connect \-\-help\fR
.br
\fBv.db.connect\fR [\-\fBpgcod\fR] \fBmap\fR=\fIname\fR  [\fBdriver\fR=\fIname\fR]   [\fBdatabase\fR=\fIname\fR]   [\fBtable\fR=\fIname\fR]   [\fBkey\fR=\fIname\fR]   [\fBlayer\fR=\fIstring\fR]   [\fBseparator\fR=\fIcharacter\fR]   [\-\-\fBoverwrite\fR]  [\-\-\fBhelp\fR]  [\-\-\fBverbose\fR]  [\-\-\fBquiet\fR]  [\-\-\fBui\fR]
.SS Flags:
.IP "\fB\-p\fR" 4m
.br
Print all map connection parameters and exit
.IP "\fB\-g\fR" 4m
.br
Print all map connection parameters in shell script style and exit
.br
Format: layer[/layer name] table key database driver
.IP "\fB\-c\fR" 4m
.br
Print types/names of table columns for specified layer and exit
.IP "\fB\-o\fR" 4m
.br
Overwrite connection parameter for certain layer
.IP "\fB\-d\fR" 4m
.br
Delete connection for certain layer (not the table)
.IP "\fB\-\-overwrite\fR" 4m
.br
Allow output files to overwrite existing files
.IP "\fB\-\-help\fR" 4m
.br
Print usage summary
.IP "\fB\-\-verbose\fR" 4m
.br
Verbose module output
.IP "\fB\-\-quiet\fR" 4m
.br
Quiet module output
.IP "\fB\-\-ui\fR" 4m
.br
Force launching GUI dialog
.SS Parameters:
.IP "\fBmap\fR=\fIname\fR \fB[required]\fR" 4m
.br
Name of vector map
.br
Or data source for direct OGR access
.IP "\fBdriver\fR=\fIname\fR" 4m
.br
Name of database driver
.br
Options: \fIdbf, mysql, odbc, ogr, pg, sqlite\fR
.br
Default: \fIsqlite\fR
.IP "\fBdatabase\fR=\fIname\fR" 4m
.br
Name of database
.br
Default: \fI$GISDBASE/$LOCATION_NAME/$MAPSET/sqlite/sqlite.db\fR
.IP "\fBtable\fR=\fIname\fR" 4m
.br
Name of attribute table
.IP "\fBkey\fR=\fIname\fR" 4m
.br
Name of key column
.br
Must refer to an integer column
.br
Default: \fIcat\fR
.IP "\fBlayer\fR=\fIstring\fR" 4m
.br
Layer number or name
.br
Format: layer number[/layer name]
.br
Default: \fI1\fR
.IP "\fBseparator\fR=\fIcharacter\fR" 4m
.br
Field separator for shell script style output
.br
Special characters: pipe, comma, space, tab, newline
.br
Default: \fIpipe\fR
.SH DESCRIPTION
\fIv.db.connect\fR prints or sets database connection for a vector
map. The user can add or remove link to attribute table on the certain
layer.
.SH NOTE
Connection information (driver, database, table, key) is stored for
each map, in the file
.br
.nf
\fC
<database>/<location>/<mapset>/vector/<map>/dbln
\fR
.fi
.PP
If parameters for database connection are already set with
db.connect, they are taken as default values and
do not need to be specified each time.
.PP
When printing database connection (\fIp\fR or \fIg\fR flag) the parameter
\fIlayer\fR is ignored, i.e. \fBall\fR connections are printed to the
output.
.PP
\fBAttention:\fR Removing a vector map will also delete all tables
linked to it! If you use v.db.connect 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 v.overlay).
.SH EXAMPLE
Note: The default database backend setting is SQLite.
.SS Print database connection
Print all database connection parameters for vector map.
.br
.nf
\fC
v.db.connect \-p map=roads
\fR
.fi
.PP
Print column types and names of table linked to vector map.
.br
.nf
\fC
v.db.connect \-c map=roads
\fR
.fi
.SS Connect vector map to database (DBF driver)
Connect vector map to DBF table without or with variables.
.br
.PP
Using default DB connection:
.br
.nf
\fC
v.db.connect map=vectormap table=table
\fR
.fi
.PP
Using hardcoded path to DBF directory (not recommended):
.br
.br
.nf
\fC
v.db.connect map=vectormap table=table \(rs
             database=/home/user/grassdata/spearfish60/PERMANENT/dbf
\fR
.fi
.PP
Using variable as DBF directory definition, single quotes must be used:
.br
.br
.nf
\fC
v.db.connect map=vectormap table=table \(rs
             database=\(cq$GISDBASE/$LOCATION_NAME/$MAPSET/dbf/\(cq
\fR
.fi
.PP
Connect vector map layer 2 and key ID to database with variables
(note: if needed, single quotes must be used for the \fIdatabase\fR
parameter):
.br
.nf
\fC
v.db.connect map=vectormap table=table layer=2 key=ID
\fR
.fi
.SS Connect vector map to database (SQLite driver)
Very similar to DBF driver example above.
.br
.nf
\fC
db.connect driver=sqlite database=\(cq$GISDBASE/$LOCATION_NAME/$MAPSET/sqlite/sqlite.db\(cq
db.tables \-p
v.db.connect map=vectormap table=table driver=sqlite \(rs
             database=\(cq$GISDBASE/$LOCATION_NAME/$MAPSET/sqlite/sqlite.db\(cq
v.db.connect \-p map=vectormap
\fR
.fi
.SS Connect vector map to database (MySQL driver)
.br
.nf
\fC
# note: connection which requires password
db.connect driver=mysql database=\(dqhost=dbserver.foo.org,dbname=my_database\(dq
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
\fR
.fi
.SS Connect vector map to database (PostgreSQL driver)
.br
.nf
\fC
# note: connection without password being asked
v.db.connect map=vectormap table=table layer=1 key=oid driver=pg \(rs
             database=\(dqhost=myserver.itc.it,dbname=mydb,user=name\(dq \(rs
             table=mytable key=id
\fR
.fi
.SS Store geometry in GRASS but attributes in PostgreSQL
This example illustrates a mixed data storage with possibility to
update attributes in an external PostgreSQL database:
.br
.nf
\fC
# 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=\(dqhost=localhost,dbname=meteo\(dq \(rs
        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 \(dqDROP TABLE mytable\(dq | db.execute
db.tables \-p
# reconnect map to table in PostgreSQL:
v.db.connect map=mytable driver=pg database=\(dqhost=localhost,dbname=meteo\(dq \(rs
        table=mytable key=cat
# Now the geometry is stored in GRASS while the attributes are stored
# in PostgreSQL.
\fR
.fi
An alternative is to create a \(dqview\(dq of only ID, x, y [,z] columns and
to use v.in.db on this view, then connect the original
table to the geometry. This will be faster if the original table
is very large.
.SS Store geometry in GRASS but attributes in PostGIS
This example illustrated a mixed data storage with possibility
top update attributes in external PostGIS database:
.br
.nf
\fC
# 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=\(dqhost=localhost,dbname=meteo\(dq \(rs
        table=mytable x=\(dqx(geom)\(dq y=\(dqy(geom)\(dq 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 \(dqDROP TABLE mytable\(dq | db.execute
db.tables \-p
# reconnect map to table in PostGIS:
v.db.connect map=mytable driver=pg database=\(dqhost=localhost,dbname=meteo\(dq \(rs
        table=mytable key=cat
# Now the geometry is stored in GRASS while the attributes are stored
# in PostGIS.
\fR
.fi
.SH SEE ALSO
\fI
db.connect,
db.copy,
db.tables,
v.db.addtable,
v.db.droptable,
v.db.addcolumn,
v.db.dropcolumn,
v.external,
v.in.db,
v.overlay
\fR
.PP
\fI
GRASS SQL interface
\fR
.SH AUTHOR
Radim Blazek, ITC\-Irst, Trento, Italy
.SH SOURCE CODE
.PP
Available at:
v.db.connect source code
(history)
.PP
Accessed: Friday Mar 08 07:35:02 2024
.PP
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.PP
© 2003\-2024
GRASS Development Team,
GRASS GIS 8.3.2 Reference Manual