The following is a simple SQL statement to create a report showing the Average Length of Stay based on past checkouts. 


SELECT MONTH(HISTHD.CHECKOUT) AS 'Mon',
             DATENAME(MONTH,HISTHD.CHECKOUT) AS 'Month',
             YEAR(HISTHD.CHECKOUT) AS 'Year',
             AVG(HISTHD.NIGHTS) AS 'Avg. Stay'

FROM HISTHD

WHERE HISTHD.CHECKOUT BETWEEN {?Select Lower And Higher Date%%}  AND  SUBSTR(HISTHD.PREVROOM, 1,1) <> '*'
GROUP BY CHECKOUT
ORDER BY 3,1
SUBTOTAL AVG(4) ON 1 HIDEDETAIL
FORMATCOLUMN 1, HIDE=1
FORMATCOLUMN 4, COLUMNPICTURE=@N_15                    
FORMATCOLUMN 4, TOTALPICTURE=@N_15