The example that you've given is basically a left join between table a and b (except you don't have any correlating conditions between table A and B) Your options are pretty simple load records from Table A and then Join the rows from table b.
something like this...
Field1 as Field3
Where Field2 = '1'
without a mathcing field between the two queries you will end up with a cartesian product so if there is a matching field or "join conditoin" you should use renaming so the names match and Qlikview will automatically join based on the matching fields.