No. We do not specifically limit the size of any of your MySQL databases.
However, the size of your MySQL databases is included in the allocation of your disk space on the server. Therefore if your hosting account provides you with 2Gb of disk space, the sum total of your files, emails and MySQL databases cannot be more than 2Gb.
When you login to cPanel you can see a summary of MySQL disk space that you are currently using on the left hand side of the screen by selecting "Expand Stats".