---
name: "v.db.join"
section: "1grass"
platform: "linux"
package: "grass-doc"
version: "8.4.1-1"
release: "Debian 13 (Trixie)"
platforms: ["linux"]
url: "https://new.carta.tech/v.db.join"
---

# v.db.join(1grass)

Joins a database table to a vector map table.

## 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

- **--verbose**

  Verbose module output

- **--quiet**

  Quiet module output

- **--ui**

  Force launching GUI dialog

### Parameters:

- **map**=*name* **\[required\]**

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

- **layer**=*string*

  Layer number or name\
   Layer where to join\
   Default: *1*

- **column**=*name* **\[required\]**

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

- **other\_table**=*name* **\[required\]**

  Other table name

- **other\_column**=*name* **\[required\]**

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

- **subset\_columns**=*name\[,name*,...\]

  Subset of columns from the other table

- **exclude\_columns**=*name\[,name*,...\]

  Columns to exclude from the other table

## DESCRIPTION

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

## NOTES

*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*.

## 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
...
```

### 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
...
```

## 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: Monday Feb 24 17:51:45 2025

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