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  DBF driver provides only very limited SQL support (as DBF is not an SQL DB) while the
       other DBMS backends (such as SQLite, PostgreSQL, MySQL etc) provide full SQL support since
       the  SQL commands are sent directly to the DBMS. For this reason, the SQLite driver is the
       default DBMI backend.

   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.

           •   Using OpenOffice.org with SQL Databases

   SQL commands
       GRASS supports two 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 SQLite tables. 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: mySQL and 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.dropcolumn.  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.connect  and  if  needed, 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 into raster data processing

           •   Introduction into 3D raster data (voxel) processing

           •   Introduction into vector data processing

           •   Introduction into image processing

           •   Introduction into temporal data processing

           •   Projections and spatial transformations

SOURCE CODE

       Available at: Database management in GRASS GIS source code (history)

       Accessed: Saturday Jul 27 11:27:22 2024

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       © 2003-2024 GRASS Development Team, GRASS GIS 8.4.0 Reference Manual