v.db.join(1)

📦
version 8.4.2 · 8 versions
, in fedora 44

💖 v.db.join(1) — GRASS GIS User's Manual 💖

okay bestie, welcome to the GRASS GIS manual, and today's main character is v.db.join(1). she joins tables. that's her whole thing. she's iconic for it. 🎀

✨ NAME ✨

v.db.join — Joins a database table to a vector map table. 🫶

🌸 KEYWORDS 🌸

vector, attribute table, database

🦋 SYNOPSIS 🦋

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,...]]
[exclude_columns=name[,name,...]]   [--help]  [--verbose]  [--quiet]
[--ui]

🎀 Flags:

  • --help — Print usage summary. literally just tells you how to use her. 💅
  • --verbose — Verbose module output. she will NOT be quiet. yapping mode: on 🗣️
  • --quiet — Quiet module output. shhh. stealth mode. 🤫
  • --ui — Force launching GUI dialog. for the girlies who love a little window moment 🪟✨

💜 Parameters:

  • map=name [required] — Name of vector map. this is the vector map you're joining the other table INTO, bestie. no map, no join, no slay. 💀
  • layer=string — Layer number or name. which layer are we joining on? Default: 1 🌈
  • column=name [required] — Identifier column (e.g.: cat) in the vector table to be used for join. this is the key she's matching on. 🔑
  • other_table=name [required] — Other table name. the table sliding into your attribute table's DMs. 💌
  • other_column=name [required] — Identifier column (e.g.: id) in the other table used for join. the key on the OTHER side. two keys, one destiny. 🔐
  • subset_columns=name[,name,...] — Subset of columns from the other table. picky picky, only want a few? valid. ✂️
  • exclude_columns=name[,name,...] — Columns to exclude from the other table. not these ones though. bye bestie 👋

🌈 DESCRIPTION 🌈

v.db.join joins the content of another table into the connected attribute table of a vector map. that's it. that's the whole vibe. she takes table B and she merges it into table A and you get one big happy table. obsessed. 💖

⭐ NOTES ⭐

v.db.join is a front-end to db.execute to allow easier usage. so she's lowkey a glamorous little wrapper. 💅

the vector attribute table must be stored in a SQL database (SQLite, PostgreSQL, MySQL, ODBC, ...). the DBF backend is not supported — nope, not happening, don't even ask. 🙈

tables can be imported with db.in.ogr. 🧚

the vector map-database connection(s) can be verified with v.db.connect. always check your connection before you commit, bestie, that's the rule. 🫶

🔥 EXAMPLES 🔥

💎 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
...

look at that output. she ATE. 🔥

🌱 Soil map table join

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
...

notice row 1|Aab||| — no match, no data, empty columns. that's just how it is sometimes, bestie. the join doesn't invent data it doesn't have. 💀

🫶 SEE ALSO 🫶

  • db.execute, db.in.ogr, db.select, v.db.update

GRASS SQL interface

👑 AUTHOR 👑

Markus Neteler

💅 SOURCE CODE 💅

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

Accessed: Saturday Jan 17 05:41:52 2026

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© 2003-2025 GRASS Development Team, GRASS GIS 8.4.2 Reference Manual

okay that's the whole page, bestie. this was GRASS 8.4.2, v.db.join(1) — © 2003-2025 GRASS Development Team, from the GRASS GIS 8.4.2 Reference Manual, accessed Saturday Jan 17 05:41:52 2026. go join something. slay. 💖✨🎀

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