What's wrong?
SELECT
ID_Contrato_Reserva,
DATE_FORMAT(STR_TO_DATE(data_ini,"%d/%m/%Y" ), "%Y/%m/%d") AS dataIni,
DATE_FORMAT(STR_TO_DATE(data_Fim,"%d/%m/%Y" ), "%Y/%m/%d") AS dataFim
FROM
contrato_reserva
WHERE
( dataIni BETWEEN "2011/09/14" AND "2012/09/14" )
AND
( dataFim BETWEEN "2011/09/17" AND "2012/09/17" )
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