grass-mysql(1grass) GRASS GIS User's Manual grass-mysql(1grass)
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 pa-
rameters 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 col-
umn(s) is used in GRASS a warning is printed and only the sup-
ported columns are returned in query results.
• Columns of type SET and ENUM are represented as string (VAR-
CHAR).
• 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 DATE-
TIME. Both types are in GRASS interpreted as TIMESTAMP.
Indexes
GRASS modules automatically create index on key column of vector at-
tributes table. The index on key column is important for performance of
modules which update the attribute table, for example v.to.db, v.dis-
tance 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 exam-
ple, 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 speci-
fied 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 re-
sult 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
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GRASS 7.8.7 grass-mysql(1grass)
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