Hi, apologies for the long response time. This is a bug in our ADQL parser. It seems to trip over the "AS c" syntax, but only when used in conjunction with mydb tables (i.e. not when used in conjunction with regular TAP tables).
We think that your query should run as-is but in sync mode (since the ADQL parser is not involved in sync queries). However, the max timeout value for sync queries is timeout=600 (seconds, i.e. 10 minutes). Can you give it a try? Maybe the timeout threshold will suffice? (please note that in unrelated news the remote file storage (vospace) is currently not working, i.e. there might be errors if you try to write out the results to a file on vospace. This should be fixed anytime soon today.)
In the meantime we are looking to fix the parser bug.
Thanks for your patience,