Use index values from your select statement (note they start at 1 not 0)

For example if you have a select statement like this:
SELECT value1, value2, value3

Replace: ORDER BY value2, value3
With: ORDER BY 2, 3

This works with MySQL and Derby

I would suggest to code like this

select
name,
dob,
title
from
(
select tblA.name,tblA.CreateDay as dob,tblA.title
from tblA

union

select tblB.name,tblB.JoiningDATE as dob,tblB.title
from tblB

) unioned -- this can be any name including yours but its a must as it works --as alias
order by dob desc


happy coding

__________________
aran