Database management in GRASS GIS

   Attribute management in general
       GRASS can be linked to one or many database management systems (DBMS).  The db.* set of commands provides
       basic  SQL  support for attribute management, while the v.db.* set of commands operates on the vector map
       (see Vector introduction).

   Available drivers
       Available drivers are listed in SQL support in GRASS GIS.

       Notes:
       The default DBF driver provides only very limited SQL support (as DBF is not an SQL DB) while  the  other
       DBMS  backends  (such  as PostgreSQL, MySQL etc) provide full SQL support since the SQL commands are sent
       directly to the DBMS.

   DB connection management
       The current database management settings are shown  or  modified  with  db.connect  for  current  mapset.
       Available  DBMI  drivers  are  listed  with  db.drivers.  Some  DBMI backends require a user/password for
       driver/database to be set with db.login.  In order to test a driver, run db.test.

   Attribute data import and export
       Attribute data can be imported with db.in.ogr from various  formats  and  exported  with  db.out.ogr.  To
       internally copy a a full table or selectively parts of it, use db.copy.

       Further conversion tools:

                     MDB Tools: Convert MS-Access data to SQL, DBF, etc.

                     Openoffice.org with SQL Databases

   SQL commands
       GRASS  supports  to main SQL operations, execution of an SQL statement (db.execute) and selection of data
       from a table (db.select).  See the SQL help page for examples.

   Managing the default DBMI settings
       Per default vector map attributes are stored in DBF table files. This default definition can be  modified
       with db.connect. If an external DBMS is used, db.login may be required.

   Creating a database
       Specific  commands are explained on the individual driver pages (these pages are only available if driver
       was compiled in this installation):

                     DBF: see DBF page

                     SQLite: SQLite page

                     mySQL: meSQL pages

                     ODBC: ODBC page  (connect to Oracle, etc.)

                     PostgreSQL: PostgreSQL and PostGIS page

   Metadata
       All columns for a given table are listed with db.columns.  The command db.describe describes a  table  in
       detail. To list all available tables for a given database, run db.tables.

   Table maintenance
       To  drop  a column from a selected attribute table, use db.dropcol.  With db.droptable an attribute table
       can be deleted.

   Database Schema
       Currently schema support  only  works  for  PostgreSQL  connections.  Default  schema  can  be  set  with
       db.connect. Note that the default schema will be used by all db.* modules.

       db.tables returns 'schema.table' if schemas are available in the database.

   Migrating to a different database engine
       To  migrate  a GRASS database table (or a GRASS vector map) to a different DBMI engine, the best solution
       is to create a new MAPSET, define the DBMI  settings  accordingly  with  db.login.   Then  the  table  of
       interest  can  be copied over with db.copy from the original MAPSET. Likewise, a vector map including its
       table(s) are copied from the original MAPSET to the current MAPSET with g.copy.

   See also
                     Introduction to GRASS vector map processing

                     Introduction to GRASS raster map processing
       Main index - database index - full index

       © 2003-2012 GRASS Development Team

GRASS 6.4.3                                                                                databaseintro(1grass)