6.19. MySQL Connector#
The MySQL connector allows querying and creating tables in an external MySQL instance. This can be used to join data between different systems like MySQL and Hive, or between two different MySQL instances.
Configuration#
To configure the MySQL connector, create a catalog properties file
in etc/catalog named, for example, mysql.properties, to
mount the MySQL connector as the mysql catalog.
Create the file with the following contents, replacing the
connection properties as appropriate for your setup:
connector.name=mysql
connection-url=jdbc:mysql://example.net:3306
connection-user=root
connection-password=secret
Multiple MySQL Servers#
You can have as many catalogs as you need, so if you have additional
MySQL servers, simply add another properties file to etc/catalog
with a different name, making sure it ends in .properties. For
example, if you name the property file sales.properties, Presto
creates a catalog named sales using the configured connector.
Decimal Type Handling#
DECIMAL types with precision larger than 38 can be mapped to a Presto DECIMAL
by setting the decimal-mapping configuration property or the decimal_mapping session property to
allow_overflow. The scale of the resulting type is controlled via the decimal-default-scale
configuration property or the decimal-rounding-mode session property. The precision is always 38.
By default, values that require rounding or truncation to fit will cause a failure at runtime. This behavior
is controlled via the decimal-rounding-mode configuration property or the decimal_rounding_mode session
property, which can be set to UNNECESSARY (the default),
UP, DOWN, CEILING, FLOOR, HALF_UP, HALF_DOWN, or HALF_EVEN
(see RoundingMode).
Querying MySQL#
The MySQL connector provides a schema for every MySQL database.
You can see the available MySQL databases by running SHOW SCHEMAS:
SHOW SCHEMAS FROM mysql;
If you have a MySQL database named web, you can view the tables
in this database by running SHOW TABLES:
SHOW TABLES FROM mysql.web;
You can see a list of the columns in the clicks table in the web database
using either of the following:
DESCRIBE mysql.web.clicks;
SHOW COLUMNS FROM mysql.web.clicks;
Finally, you can access the clicks table in the web database:
SELECT * FROM mysql.web.clicks;
If you used a different name for your catalog properties file, use
that catalog name instead of mysql in the above examples.
MySQL Connector Limitations#
The following SQL statements are not yet supported: