Código:
SELECT `id_ficha` FROM `TEstancia` INNER JOIN 'TCliente' ON ('TCliente'.DNI = 'TEstancia'.numDNI)
#1064 - You have an error in your SQL syntax. Check the manual that corresponds to your MySQL server version for the right syntax to use near ''TCliente' ON ('TCliente'.DNI = 'TEstancia'.numDNI)
LIMIT 0, 3