Hi, thanks for reaching out. I suppose you mean the web-based query tool? Accessing mydb tables is currently not supported using the web query interface. Please use either the Jupyter notebook server, or, if you install the astro-datalab pip package on your local computer, you can also run queries against your mydb from your local machine.
An example query:
from dl import queryClient as qc
df = qc.query("select * from mydb://mytable001 limit 100", fmt='pandas') # default fmt is 'csv')
Hope this is helpful,
Robert