trusty (1) databaseintro.1grass.gz

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