Union on two tables with a where clause in the one

Question

Currently I have 2 tables, both of the tables have the same structure and are going to be used in a web application. the two tables are production and temp. The temp table contains one additional column called [signed up]. Currently I generate a single list using two columns that are found in each table (recno and name). Using these two fields I'm able to support my web application search function. Now what I need to do is support limiting the amount of items that can be used in the search on the second table. the reason for this is become once a person is "signed up" a similar record is created in the production table and will have its own recno.

doing:

Select recno, name
  from production
UNION ALL
Select recno, name
  from temp

...will show me everyone. I have tried:

Select recno, name
  from production
UNION ALL
Select recno, name
  from temp
 WHERE signup <> 'Y'

But this returns nothing? Can anyone help?

Answer 1

For what you are asking, you could do it this style.

SELECT * FROM
(
    SELECT '1' as `col`
    UNION 
    SELECT '2' as `col`
) as `someAlias`
where `someAlias`.`col` = '1'

Put the entire union inside parenthesis, give it an alias, then give the condition.