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ODBC driver in GRASS

Communication between GRASS and ODBC database for attribute management:

GRASS module <->	<-->	ODBC Interface	<-->	RDBMS
GRASS	DBMI driver	unixODBC	ODBC driver	PostgreSQL
				Oracle
				...

Supported SQL commands

All SQL commands supported by ODBC.

Operators available in conditions

All SQL operators supported by ODBC.

EXAMPLE

In this example we copy the dbf file of a SHAPE map into ODBC, then connect GRASS to the ODBC DBMS. Usually the table will be already present in the DBMS.

Defining the ODBC connection

MS-Windows

On MS-Windows, in order to be able to connect, the ODBC connection needs to be configured using dedicated tools (tool called "ODBC Data Source Administrator") and give a name to that connection. This name is then used as database name when accessing from a client via ODBC.

Linux

Configure ODBC driver for selected database (manually or with 'ODBCConfig'). ODBC drivers are defined in /etc/odbcinst.ini. Here an example:

 [PostgreSQL]
 Description     = ODBC for PostgreSQL
 Driver          = /usr/lib/libodbcpsql.so
 Setup           = /usr/lib/libodbcpsqlS.so
 FileUsage       = 1

Create DSN (data source name). The DSN is used as database name in db.* modules. Then DSN must be defined in $HOME/.odbc.ini (for this user only) or in /etc/odbc.ini for (for all users) [watch out for the database name which appears twice and also for the PostgreSQL protocol version]. Omit blanks at the beginning of lines:

 [grass6test]
 Description             = PostgreSQL
 Driver                  = PostgreSQL
 Trace                   = No
 TraceFile               =

 Database                = grass6test
 Servername              = localhost
 UserName                = neteler
 Password                =
 Port                    = 5432
 Protocol                = 8.0 

 ReadOnly                = No
 RowVersioning           = No
 ShowSystemTables        = No
 ShowOidColumn           = No
 FakeOidIndex            = No
 ConnSettings            =

Configuration of an DSN without GUI is described on http://www.unixodbc.org/odbcinst.html, but odbc.ini and .odbc.ini may be created by the 'ODBCConfig' tool. You can easily view your DSN structure by 'DataManager'. Configuration with GUI is described on http://www.unixodbc.org/doc/UserManual/

To find out about your PostgreSQL protocol, run:

psql -V

Using the ODBC driver

Now create a new database if not yet existing:

db.createdb driver=odbc database=grass6test

To store a table 'mytable.dbf' (here: in current directory) into PostgreSQL through ODBC, run:

db.connect driver=odbc database=grass6test
db.copy from_driver=dbf from_database=./ from_table=mytable \
        to_driver=odbc to_database=grass6test to_table=mytable

Next link the map to the attribute table (now the ODBC table is used, not the dbf file):

v.db.connect map=mytable.shp table=mytable key=ID \
             database=grass6test driver=odbc
v.db.connect -p

Finally a test: Here we should see the table columns (if the ODBC connection works):

db.tables -p
db.columns table=mytable

Now the table name 'mytable' should appear.
Doesn't work? Check with 'isql <databasename>' if the ODBC-PostgreSQL connection is really established.

Note that you can also connect mySQL, Oracle etc. through ODBC to GRASS.

You can also check the vector map itself concerning a current link to a table:

v.db.connect -p mytable.shp

which should print the database connection through ODBC to the defined RDBMS.