ODBC DATABASE DRIVER

Supported SQL commands
Operators available in conditions
EXAMPLE
- Defining the ODBC connection
- Using the ODBC driver
SEE ALSO

Communication between GRASS and ODBC database for attribute management:

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

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.

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.