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.

## SEE ALSO

db.connect, v.db.connect, unixODBC web site, SQL support in GRASS GIS

Last changed: $Date$