SELECT
INQUI."País",
COUNT(*) AS RESERVAS."Reservas$SUM",
AVG(RESERVAS.Desde-RESERVAS."Fecha realizada") AS RESERVAS."Antelación media"
FROM
RESERVAS,
INQUI
WHERE
RESERVAS.Desde >= ':1'
AND RESERVAS.Desde <= ':2'
AND RESERVAS.Agencia >= -1
AND INQUI."Código"=RESERVAS.Inquilino
GROUP BY
INQUI."País"
ORDER BY
INQUI."País"