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MySQL DATABASE DRIVER

       MySQL database driver enables GRASS to store vector attributes in MySQL server.

       Because vector attribute tables are created automatically when a new vector is written and
       the name of the table is the same as the name of the vector it is good practice to  create
       a new database for each GRASS mapset.

Creating a MySQL database

       A new database is created within MySQL:
       mysql> CREATE DATABASE mydb;
       See the MySQL manual for details.

Driver and database name

       GRASS  modules  require  2  parameters  to  connect  to  a database.  Those parameters are
       ’driver’ and ’database’. For MySQL driver the parameter ’driver’ should be  set  to  value
       ’mysql’.  The parameter ’database’ can be given in two formats:

           ·   Database name - in case of connection from localhost

           ·   String of comma separated list of kye=value options.  Supported options are:

               ·   dbname - database name

               ·   host - host name or IP address

               ·   port - server port number
       Examples of connection parameters:
         db.connect driver=mysql database=mytest
         db.connect driver=mysql database=’dbname=mytest,host=test.grass.org’

Data types

       GRASS supports almost all MySQL data types with following limitations:

           ·   Binary  columns  (BINARY, VARBINARY, TINYBLOB, MEDIUMBLOB, BLOB, LONGBLOB) are not
               not supported.  If a table with binary column(s) is used in  GRASS  a  warning  is
               printed and only the supported columns are returned in query results.

           ·   Columns of type SET and ENUM are represented as string (VARCHAR).

           ·   Very  large  integers  in  columns of type BIGINT can be lost or corrupted because
               GRASS does not support 64 bin integeres on most platforms.

           ·   GRASS does not currently distinguish types TIMESTAMP and DATETIME. Both types  are
               in GRASS interpreted as TIMESTAMP.

Indexes

       GRASS  modules  automatically  create  index on key column of vector attributes table. The
       index on key column is important for performance of modules  which  update  the  attribute
       table, for example v.to.db, v.distance and v.what.rast.

Privileges

       Because  MySQL  does  not  support groups of users and because only MySQL ’root’ can grant
       privileges to other users GRASS cannot automatically grant select  privileges  on  created
       tables to group of users.

       If you want to give privilege to read data from your mapset to other users you have to ask
       your MySQL server administrator to grant select privilege to them on  the  MySQL  database
       used  for that mapset. For example, to allow  everybody to read data in from your database
       ’mydb’:
       shell> mysql --user=root mysql
       mysql> GRANT SELECT ON mydb.* TO ’’@’%’;

Schemas

       Because MySQL  does  not  support  database  schemas  the  parameter  ’schema’  of  module
       db.connect  should  never  be set to any value. If you set that parameter for MySQL driver
       GRASS will try to write tables to the specified schema which will result in errors.

Groups

       MySQL does not support user groups. Any settings specified by ’group’ parameter of  module
       db.connect are ignored by GRASS for MySQL driver.

Troubleshooting: SQL syntax error

       Attempting  to  use  a  reserved  SQL  word  as column or table name will result in a "SQL
       syntax" error. The list of reserved words for MySQL can be found in the MySQL manual.

SEE ALSO

        db.connect, SQL support in GRASS GIS

Credits

       Development of the driver was sponsored by Faunalia (Italy) as part of a project for ATAC.

AUTHOR

       Radim Blazek

       Last changed: $Date: 2014-04-20 12:28:15 +0200 (Sun, 20 Apr 2014) $

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