If I use apache drill and connect to a RDBMS like MySQL will I be able to utilize full SQL syntax (like UPDATE/INSERT)?
I have seen this answer regarding UPDATE/INSERT on HDFS, wonder if these is any difference when using drill with RDBMSs.
No it is not supported. You can think of Drill as a SQL engine, not a database. A SQL engine is intended to execute a select statement on a large amount of data as quickly as possible so that the user can answer a question about their data. A database is a SQL engine with extra data management functionality like inserts and updates.
Typically people use Drill on data that is no longer changing. For example if you are running a website and you have data about user activity yesterday. That dataset is no longer changing but you can execute SQL on that data to answer your questions.