Pentaho Data Integration SQL connection

I just came across the same issue while trying to query a MySQL Database from Pentaho.

Error connecting to database [Local MySQL DB] : org.pentaho.di.core.exception.KettleDatabaseException:
Error occured while trying to connect to the database

Exception while loading class
org.gjt.mm.mysql.Driver

Expanding post by @user979331 the solution is:

1. Download the MySQL Java Connector / Driver that is compatible with your kettle version
2. Unzip the zip file (in my case it was mysql-connector-java-5.1.31.zip)

3. copy the .jar file (mysql-connector-java-5.1.31-bin.jar) and paste it in your Lib folder:

   PC: C:\Program Files\pentaho\design-tools\data-integration\lib

   Mac: /Applications/data-integration/lib

Restart Pentaho (Data Integration) and re-test the MySQL Connection.

Additional interesting replies from others that could also help:

• think to download the good JDBC driver version, compatible with your
  PDI version:
  https://help.pentaho.com/Documentation/8.1/Setup/JDBC_Drivers_Reference#MY_SQL
• take the zip version (“platform independant”) to extract the jar file
• take into lib folder
• see also proper way to handle it proposed by Ryan Tuck