.TH v.db.join 1grass "" "GRASS 7.8.5" "GRASS GIS User's Manual"
.SH NAME
\fI\fBv.db.join\fR\fR  \- Joins a database table to a vector map table.
.SH KEYWORDS
vector, attribute table, database
.SH SYNOPSIS
\fBv.db.join\fR
.br
\fBv.db.join \-\-help\fR
.br
\fBv.db.join\fR \fBmap\fR=\fIname\fR  [\fBlayer\fR=\fIstring\fR]  \fBcolumn\fR=\fIname\fR \fBother_table\fR=\fIname\fR \fBother_column\fR=\fIname\fR  [\fBsubset_columns\fR=\fIname\fR[,\fIname\fR,...]]   [\-\-\fBhelp\fR]  [\-\-\fBverbose\fR]  [\-\-\fBquiet\fR]  [\-\-\fBui\fR]
.SS Flags:
.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
Vector map to which to join other table
.IP "\fBlayer\fR=\fIstring\fR" 4m
.br
Layer number or name
.br
Layer where to join
.br
Default: \fI1\fR
.IP "\fBcolumn\fR=\fIname\fR \fB[required]\fR" 4m
.br
Identifier column (e.g.: cat) in the vector table to be used for join
.IP "\fBother_table\fR=\fIname\fR \fB[required]\fR" 4m
.br
Other table name
.IP "\fBother_column\fR=\fIname\fR \fB[required]\fR" 4m
.br
Identifier column (e.g.: id) in the other table used for join
.IP "\fBsubset_columns\fR=\fIname[,\fIname\fR,...]\fR" 4m
.br
Subset of columns from the other table
.SH DESCRIPTION
\fIv.db.join\fR joins the content of another table into the connected
attribute table of a vector map.
.SH NOTES
\fIv.db.join\fR is a front\-end to \fIdb.execute\fR to allow easier usage.
The vector attribute table must be stored in a SQL database (SQLite, PostgreSQL,
MySQL, ODBC, ...). The DBF backend is not supported. Tables can be
imported with \fIdb.in.ogr\fR.
.PP
The vector map\-database connection(s) can be verified with \fIv.db.connect\fR.
.SH EXAMPLES
Exercise to join North Carolina geological classes from a CSV table to
the \(dqgeology\(dq map of the North Carolina sample dataset (requires download
of legend CSV file nc_geology.csv
from External data for NC sample dataset):
.br
.nf
\fC
# check original map attributes
v.db.select geology column=GEO_NAME,SHAPE_area
# import of CSV table
db.in.ogr input=nc_geology.csv output=nc_geology
# work on copy of geology map in current mapset
g.copy vector=geology,mygeology
# check column names of vector map attributes
v.info \-c mygeology
# check column names of legend table
db.describe \-c nc_geology
# join table using key columns (map: \(dqGEO_NAME\(dq; table: \(dqgeol_id\(dq)
v.db.join map=mygeology column=GEO_NAME other_table=nc_geology other_column=geol_id
# verify result (here abbreviated)
v.db.select mygeology | head \-3
cat|onemap_pro|PERIMETER|GEOL250_|GEOL250_ID|GEO_NAME|SHAPE_area|SHAPE_len|geol_id|longname|comment
1|963738.75|4083.97998|2|1|Zml|963738.608571|4083.979839|Zml|Metagraywacke|Interlayered with metaconglomerate, ...
2|22189124|26628.261719|3|2|Zmf|22189123.2296|26628.261112|Zmf|Metafelsite|Light\-colored porphyritic extrusive rock
\&...
\fR
.fi
.SS Soil map table join
Joining the soil type explanations from table \fIsoils_legend\fR
into the Spearfish soils map (download legend):
.br
.nf
\fC
g.copy vect=soils,mysoils
# import legend table
db.in.ogr soils_legend.csv out=soils_legend
# get join column names
v.info \-c mysoils
db.describe \-c soils_legend
# look at original table
v.db.select mysoils
cat|label
1|Aab
2|Ba
3|Bb
4|BcB
5|BcC
\&...
# look at legend
db.select table=soils_legend
db.select table=soils_legend | head \-7
id|shortname|longname
0|no data|no data
0|AaB|Alice fine sandy loam, 0 to 6
0|Ba|Barnum silt loam
0|Bb|Barnum silt loam, channeled
0|BcB|Boneek silt loam, 2 to 6
0|BcC|Boneek silt loam, 6 to 9
\&...
# join soils_legend into mysoils attribute table
v.db.join mysoils col=label other_table=soils_legend ocol=shortname
# verification of join
v.db.select mysoils
cat|label|id|shortname|longname
1|Aab|||
2|Ba|2|Ba|Barnum silt loam
3|Bb|3|Bb|Barnum silt loam, channeled
4|BcB|4|BcB|Boneek silt loam, 2 to 6
5|BcC|5|BcC|Boneek silt loam, 6 to 9
\&...
\fR
.fi
.SH SEE ALSO
\fI
db.execute,
db.in.ogr,
db.select,
v.db.update
.br
GRASS SQL interface
\fR
.SH AUTHOR
Markus Neteler
.SH SOURCE CODE
.PP
Available at: v.db.join source code (history)
.PP
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.PP
© 2003\-2020
GRASS Development Team,
GRASS GIS 7.8.5 Reference Manual