Ubuntu Manpage: grass-dbf

NAME

       grass-dbf - DBF driver

       DBF driver DBF driver in GRASS

Defining the DBF driver

       The DBF driver is the default driver, in theory no user interaction is required. However, if the settings
       should be set back from a different to the DBF driver, the following step is required:
       # keep single quotes:
       db.connect driver=dbf database='$GISDBASE/$LOCATION_NAME/$MAPSET/dbf/'
       db.connect -p
        The dbf/ subdirectory in the mapset must exist or must be created by the user.

Creating a DBF table

       Usually  DBF  tables  are created by GRASS when generating a vector map with attributes (and using DBF as
       default attribute driver).

       If a DBF table has to be created manually, db.execute can be used  or  a  spreadsheet  application.  Also
       db.copy is sometimes useful as well as db.in.ogr to import external tables.

Supported SQL commands by DBF driver


         ALTER TABLE table ADD [COLUMN] columndef
         ALTER TABLE table DROP COLUMN colname
         CREATE TABLE table ( columndefs )
         DROP TABLE table
         SELECT columns FROM table
         SELECT columns FROM table WHERE condition
         SELECT columns FROM table ORDER BY column
         DELETE FROM table
         DELETE FROM table WHERE condition
         INSERT INTO table VALUES (value1[,value2,...])
         INSERT INTO table ( column1[,column2,...] ) VALUES (value1[,value2,...])
         UPDATE table SET assignment1[,assignment2,...]
         UPDATE table SET assignment1[,assignment2,...] WHERE condition

Operators available in conditions


         "="  : equal
         "<"  : smaller than
         "<=" : smaller/equal than
         ">"  : larger than
         ">=" : larger/equal than
         "<>" : not equal
         "~"  : Substring matching  (non-standard SQL)
         "%"  : Substring matching  (limited functionality)

       Arithmetic  expressions  using constants and field values are allowed in condition clauses and in the RHS
       of assignments.
       Usual precedence rules and bracketing (using '(' and ')') are supported.
       Type conversion is performed if necessary (experimental).

       Conditions allow boolean expressions using the AND, OR and  NOT  operators,  with  the  usual  precedence
       rules.

       NULLs can be tested by 'colname IS NULL' in conditions. The negation is ’colname NOT NULL'.

       Sorting: Empty fields in a character column are sorted to the end.

LIMITATIONS OF THE DBF DRIVER

       The  DBF  driver  supports  only  a few SQL statements since the DBF tables are intended for simple table
       storage. DBF column names are limited to 10 characters  (as  defined  in  the  DBF  specifications).  For
       example,

                      aggregate functions (sum, count, min, max,...) are not supported in SELECT clauses;

                      mathematic functions (sin, cos, exp, log,...) are not supported in expressions;

                      SQL query with IN are not supported.

ERROR MESSAGES

       An error message such as:
       DBMI-DBF driver error:
       SQL parser error: syntax error, unexpected NAME processing 'IN'..
         indicates  that  an unsupported SQL statement (here, 'IN') was used. The only solution is to switch the
       DBMI backend to a real SQL engine (SQLite, PostgreSQL, MySQL etc.). See SQL support in GRASS GIS.

       An error message such as:
       DBMI-DBF driver error:
       SQL parser error: syntax error, unexpected DESC, expecting NAME processing 'DESC'
        indicates that a column name corresponds to a reserved SQL word (here: 'DESC').  A different column name
       should be used. If this happens during import with v.in.ogr, the cnames parameter can be used  to  assign
       different column names on the fly.

NAME

Defining the DBF driver

Creating a DBF table

Supported SQL commands by DBF driver

Operators available in conditions

LIMITATIONS OF THE DBF DRIVER

ERROR MESSAGES

SEE ALSO