Um.
10 Nov 2014 fails the '2014-12-01' <= a.From_Date but passes the '2014-12-01' >= a.From_Date
10 Dec 2014 passes the '2014-12-01' <= a.From_Date but fails the '2014-12-01' >= a.From_Date
10 Jan 2014 passes the '2014-12-01' <= a.From_Date but fails the '2014-12-01' >= a.From_Date
So any data at all will pass some part of your condition, it depends on the "to date" whether the whole will pass.
Isn't what you want really just :
'2014-12-01' BETWEEN a.From_Date AND a.To_Date