db.select - GRASS GIS manual

NAME

db.select - Selects data from attribute table.
Performs SQL query statement(s).

KEYWORDS

SYNOPSIS

db.select

db.select --help

db.select [-cdvt] [sql=sql_query] [input=name] [table=name] [driver=name] [database=name] [separator=character] [vertical_separator=character] [null_value=string] [output=name] [--overwrite] [--help] [--verbose] [--quiet] [--ui]

Flags:

-c: Do not include column names in output
-d: Describe query only (don't run it)
-v: Vertical output (instead of horizontal)
-t: Only test query, do not execute
--overwrite: Allow output files to overwrite existing files
--help: Print usage summary
--verbose: Verbose module output
--quiet: Quiet module output
--ui: Force launching GUI dialog

Parameters:

sql=sql_query: SQL SELECT statement; Example: select * from towns where population > 10000
input=name: Name of file containing SQL select statement(s); '-' for standard input
table=name: Name of table to query
driver=name: Name of database driver; Options: dbf, odbc, ogr, pg, sqlite; Default: sqlite
database=name: Name of database; Default: $GISDBASE/$LOCATION_NAME/$MAPSET/sqlite/sqlite.db
separator=character: Field separator; Special characters: pipe, comma, space, tab, newline; Default: pipe
vertical_separator=character: Vertical record separator (requires -v flag); Special characters: pipe, comma, space, tab, newline
null_value=string: String representing NULL value
output=name: Name for output file (if omitted or "-" output to stdout)

DESCRIPTION
NOTE
EXAMPLES
SEE ALSO
AUTHORS

DESCRIPTION

db.select prints result of selection from database based on SQL statement read from input file or from standard input to standard output. Each individual query has to be written on one single line and different queries have to be written on separate lines.

NOTE

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. Output will be displayed to standard output or can be directed to a file (option output).

EXAMPLES

Basic usage

db.select sql="select * from roads"

echo "select * from roads" | db.select input=-

db.select input=file.sql

cat file.sql | db.select input=-

Select all from table roads:

db.select -c driver=odbc database=mydb table=hospitals \
          input=file.sql output=result.csv

Select some string attribute, exclude others:

db.select sql="SELECT * FROM archsites WHERE str1 <> 'No Name'"

Select some string attribute with ZERO length:

db.select sql="SELECT * FROM archsites WHERE str1 IS NULL"

Select coordinates from PostGIS table:

db.select sql="SELECT x(geo),y(geo) FROM localizzazione"

Execute multiple SQL statements

cat file.sql
SELECT * FROM busstopsall WHERE cat = 1
SELECT cat FROM busstopsall WHERE cat > 4 AND cat < 8

db.select input=file.sql

Count number of cases falling into same position

When multiple observation have the spatial coordinates, they can still be counted (if needed, coordinates can be uploaded to the attribute table by v.to.db:

db.select sql="SELECT long,lat,site_id,department,obs,COUNT(long) as count_cases \
               FROM diseases GROUP BY long,lat"

AUTHORS

Original author unknown (probably CERL)
Modifications by Radim Blazek, ITC-Irst, Trento, Italy
Support for multiple statements by Martin Landa, Czech Technical University in Prague

SOURCE CODE

Available at: db.select source code (history)

Latest change: Wednesday Nov 27 22:53:26 2024 in commit: b90ce69e88409469369ec1edb86fde8ec822af8b