Puede usar paréntesis para permitir el uso de ORDER
/LIMIT
en consultas individuales:
(SELECT * FROM some tables WHERE ... ORDER BY field1 LIMIT 0, 1)
UNION
(SELECT * FROM some tables WHERE ...)
ORDER BY 1 /* optional -- applies to the UNIONed result */
LIMIT 0, 100 /* optional -- applies to the UNIONed result */