@Someswara Durga Prasad Yaralgadda​ :

The NoClassDefFoundError error occurs when a class that was available during the compile time is not available at the runtime. This could be due to a few reasons, including a missing dependency or an incompatible version of a dependency.

In your case, it seems like the error is related to the Azure SQL DB Spark connector library. The missing class could be a part of this library. You can try the following steps to resolve the issue:

1. Check that the necessary Azure SQL DB Spark connector library is available in your cluster's runtime environment. You can try to add the dependency explicitly using the %AddJar magic command.
2. Make sure that the version of the Azure SQL DB Spark connector library matches the version that is compatible with your Spark cluster's runtime version.