You will need to provide more details.
Why do you want to get data from two unrelated tables with one single query ?
To get data from 2 or more tables with 1 query you could use a JOIN query, but you will need at least one column to join them on (tables must be related in some way, or you would get a cartesian product).
You could also use a UNION if columns in both tables are similar (columns requested from one table must match columns requested from the second table in number and types).
Please explain your situation with more details, and post your table structures (and some example data if possible), so we can better help you.