Depends on how you want to join them. You can use a union query that will return all records in both queries however the Select clauses in both must A. Contain the same number of fields and b they must be the same type for Example:
Code:
Select Month(datefield), Sum(Sales) As Total Sales, "Sales" as type
From atable
Union All
Select Month(datefield, Sum(projectedSales), "Projected"
From btable
A bit simplistic I know but the principle is the same regardless of how many tables and joins there are in the query.
Secondly If theres a link between query 1 and query 2 just put all of the fields from both in the select and make the appropriate joins in the from. If there is no link combining the 2 queries will give you a cartesian product which means if Query A Returns 10 Records and Query B returns 10 Records the combined query will return 100 Records.