EXPERT RESPONSE
You're right that "SELECT FieldName FROM table6, table7, table8 WHERE
Condition" won't work for several reasons -- at the very least,
you'll end up with a gazillion useless rows, because without a
join condition you'll get all possible combinations
of all rows from all the tables; this is called a cross join.
The tables are probably not even joinable, which is to say that
although you can cross-join them, it doesn't make sense to.
Try a UNION. This allows you to select rows from each table
individually, and merge all the resulting rows together into
one result set.
select FieldName
from table6
where Condition='1'
union
select FieldName
from table7
where Condition='1'
union
select FieldName
from table8
where Condition='1'
If you use UNION, then any duplicate FieldName values,
coming from more than one of the subselects,
will be merged into one result row. If you want to preserve
the individual (duplicate) values in the result set, use UNION ALL.
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