Different results between date and Cast As Date - sql-server

Question

I'm new to the T-SQl world and this issue is puzzling me.
I'm running a query against a variable I have created which holds the date of the start of my financial year, which is 2014-04-01. The data I'm querying against holds the date as a date time field, so I have been using CAST AS DATE to remove the timestamp.
If I run this query in this fashion I receive 25 results:
select count(B.WorkOrderNumber) as AWOCount
from TSP1_Dev.AssetDataPortal.EllipseSiteList A left outer join
TSP1_Dev.AssetDataPortal.tblWorkOrdersActive B
on A.EquipmentLocation = B.EquipmentLocation
where
B.EquipmentLocation = 'BISHT'
and A.EquipmentClass = 'SW'
and right(rtrim(A.EquipmentDesc),4) = '(OU)'
and cast(B.CreationDate as Date) >= '2014-04-01';
However, on one occasion I forgot to cast the date, and when I did that I received 32 results:
select count(B.WorkOrderNumber) as AWOCount
from TSP1_Dev.AssetDataPortal.EllipseSiteList A left outer join
TSP1_Dev.AssetDataPortal.tblWorkOrdersActive B
on A.EquipmentLocation = B.EquipmentLocation
where
B.EquipmentLocation = 'BISHT'
and A.EquipmentClass = 'SW'
and right(rtrim(A.EquipmentDesc),4) = '(OU)'
and B.CreationDate >= '2014-04-01';
Can someone please tell me why? Apologies for my ignorance!
Neil

Answer 1

In the query you have string literals and from your comment I can only assume that it is Coldfusion that insert the string literal in your query. (I know nothing about Coldfusion but is there no way to use parameters instead?).
In SQL Server there is a setting for the order of date parts in strings. SET DATEFORMAT
What you see can be reproduced if you have the date format dmy.
The string literal 2014-04-01 is interpreted as yyyy-dd-mm when compared against a datetime. When the new data types date and datetime2 was added that behaviour was changed so string literal on the form yyyy-mm-dd will always be interpreted as just that regardless of set dateformat.
So when you cast to date the string literal is converted to the date 2014-04-01 but when you compare against a datetime the string literal is converted to 2014-01-04.
set dateformat dmy;
declare #T table(D datetime);
insert into #T(D) values
('20140101'),('20140201'),
('20140301'),('20140401'),
('20140501'),('20140601');
select count(*)
from #T
where D >= '2014-04-01';
select count(*)
from #T
where cast(D as date) >= '2014-04-01';
Result:
5
3
One way to avoid the problem for datetime is to use a string literal without dashes. 20140401 will be interpreted as yyyymmdd regardless of set dateformat.