We can configure MySQL in Liferay very easily. The configuration for MySQL is done in the properties file named as "portal-ext.properties".

You just need to follow the below steps:

1. If portal-ext.properties is not available then you can manually create portal-ext.properties file into the /tomcat-7.0.42/webapps/ROOT/WEB-INF/classes/ floder of your Liferay Tomcat Bundle.

2. Write the below contents in the portal-ext.properties file

   jdbc.default.driverClassName=com.mysql.jdbc.Driver
   jdbc.default.url=jdbc:mysql://localhost:3306/dentalnote?useUnicode=true&characterEncoding=UTF-8&useFastDateParsing=false
   jdbc.default.username=root
   jdbc.default.password=test

   In the above case mysql user name is root and password is test. You need to provide proper mysql credentials according to your mysql setup. And dentalnote is the database that we are connecting with Liferay .

3. Now restart your liferay tomcat server to connect to MySQL.

Hope this will help you :)