i have a table with following columns

id
startDate = 25/11/2012
endDate = 27/11/2012
timeFrom = 11.5
timeTo = 12

date format is DD/MM/YYYY
and value 11.5 means 11:30
but we are storing it as 11.5 in database
like

9.5
10.5
11.5
12.5
13.5
14.5
15.5

my problem is, i want one sql query that can take out the records of users who are not available for the given time.

i have varchar(50) for all the columns