I have a stored procedure along the lines of

SELECT ID, Amount1, Amount2 ..

FROM Table1.

UNION

SELECT ID, Amount1, Amount2...

FROM Table2

ORDER BY 1

Is it possible to construct a conditional ORDER By clause that orders by Amount1 under certain conditions, and order by Amount2 under other conditions?

At the moment, the only way around it I have found (and I spent most of the night trying!) is to use an If clause and duplicate nearly all the SQL

IF (Condition1) THEN

SELECT ID, Amount1, Amount2 ..

FROM Table1.

UNION

SELECT ID, Amount1, Amount2...

FROM Table2

ORDER BY 1