How to select from multiple tables without a JOIN

Question

What is the simplest way to choose data from two tables and have them show up as distinct rows rather than being joined? Both tables have fields that are the same or comparable, and I want to do an aggregate operation on them, such as averaging all the rows from both tables that occurred in the same month.

I have two tables, for instance, one of which displays transactions from one system and the other of which displays transactions from a different system. Is it possible to extract each transaction from the two tables as a distinct row? I would like the return to include 50 rows if table 1 contained 20 records and table 2 contained 30 records.

Answer 1

Try this:

SELECT ...
FROM (
    SELECT f1,f2,f3 FROM table1
    UNION
    SELECT f1,f2,f3 FROM table2
)
WHERE ...

I hope this helps you.

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