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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.

       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

   Attribute data import and export
       Attribute data can be imported with  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.

            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 (  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

       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

   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

       Last changed: $Date: 2009-04-14 21:26:25 +0200 (Tue, 14 Apr 2009) $

       © 2008 GRASS Development Team