DOKK / manpages / debian 10 / grass-doc / v.db.join.1grass.en
v.db.join(1grass) Grass User's Manual v.db.join(1grass)

v.db.join - Joins a database table to a vector map table.

vector, attribute table, database

v.db.join
v.db.join --help
v.db.join map=name [layer=string] column=name other_table=name other_column=name [subset_columns=name[,name,...]] [--help] [--verbose] [--quiet] [--ui]


Print usage summary

Verbose module output

Quiet module output

Force launching GUI dialog


Name of vector map
Vector map to which to join other table

Layer number or name
Layer where to join
Default: 1

Identifier column (e.g.: cat) in the vector table to be used for join

Other table name

Identifier column (e.g.: id) in the other table used for join

Subset of columns from the other table

v.db.join joins the content of another table into the connected attribute table of a vector map.

v.db.join is a front-end to db.execute 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 db.in.ogr.

The vector map-database connection(s) can be verified with v.db.connect.

Exercise to join North Carolina geological classes from a CSV table to the "geology" map of the North Carolina sample dataset (requires download of legend CSV file nc_geology.csv from External data for NC sample dataset): 

# 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: "GEO_NAME"; table: "geol_id")
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
...

Joining the soil type explanations from table soils_legend into the Spearfish soils map (download legend): 

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
...

db.execute, db.in.ogr, db.select, v.db.update
GRASS SQL interface

Markus Neteler

Last changed: $Date: 2015-12-17 15:38:13 +0100 (Thu, 17 Dec 2015) $

Available at: v.db.join source code (history)

Main index | Vector index | Topics index | Keywords index | Graphical index | Full index

© 2003-2019 GRASS Development Team, GRASS GIS 7.6.0 Reference Manual

GRASS 7.6.0