I just blocked the port and kept on serving....
As of yet, no one has mentioned the port. Out of curiosity, is it included in the Reduced Exit Policy? https://trac.torproject.org/projects/tor/wiki/doc/ReducedExitPolicy
I cannot say. However it may be as simple as blocking sql's default port. Why exit to them anyways, as opposed to 80, 443, 22, 25 which are fairly obvious keepers. mysql 3306 postgres 5432 ms 1433/1434 etc