Using a DateTime as paramter in stored procedures, conversion failed - stored-procedures

Question

I have created a stored procedure that takes a single DATETIME as its input parameter. When I try to pass in a date in the format of MM-DD-YYYY OR YYYY-MM-DD I get the error
Conversion failed when converting date and/or time from character string.
The date I am testing with is 2010-01-01 and if I take that and plug it right into the select statement from the stored procedure it woks fine. What do I have to do to use a DATETIME as a parameter?
Here is my code:
CREATE PROC dbo.WSL_ProjectSearchByDate
#param1 DATETIME --Search Date
AS
SET NOCOUNT ON;
DECLARE #STMT NVARCHAR(MAX)
SET #STMT =
'SELECT project AS Project,
project_desc AS Description
status_gl AS Status
FROM dbo.PJPROJ WITH (NOLOCK)
WHERE crtd_datetime >= ' + #param1 + '
OR lupd_datetime >= ' + #param1 + ';';
EDIT: I am fully aware this is not best practice to be using dynamic SQL, I don't have any say in the matter and this question is not about the merits of dynamic SQL and whether or not I should be using it. This is how I have been instructed to build my stored procedures and so I am doing that.

Answer 1

Change the parameter type to VARCHAR and add quotes to your dynamic SQL:
...
#param1 VARCHAR(10) --Search Date
...
WHERE crtd_datetime >= ''' + #param1 + '''
OR lupd_datetime >= ''' + #param1 + ''';';
or -
Apply a CONVERT to your parameter when constructing your dynamic SQL:
...
WHERE crtd_datetime >= ''' + CONVERT(VARCHAR, #param1, 120) + '''
OR lupd_datetime >= ''' + CONVERT(VARCHAR, #param1, 120) + ''';';

Answer 2

Various settings (language, date format) only influence how the DateTime is shown to you in SQL Server Management Studio - or how it is parsed when you attempt to convert a string to a DateTime.
There are many formats supported by SQL Server - see the MSDN Books Online on CAST and CONVERT. Most of those formats are dependent on what settings you have - therefore, these settings might work some times - and sometimes not.
The way to solve this is to use the (slightly adapted) ISO-8601 date format that is supported by SQL Server - this format works always - regardless of your SQL Server language and dateformat settings.
The ISO-8601 format is supported by SQL Server comes in two flavors:
YYYYMMDD for just dates (no time portion); note here: no dashes!, that's very important! YYYY-MM-DD is NOT independent of the dateformat settings in your SQL Server and will NOT work in all situations!
or:
YYYY-MM-DDTHH:MM:SS for dates and times - note here: this format has dashes (but they can be omitted), and a fixed T as delimiter between the date and time portion of your DATETIME.
This is valid for SQL Server 2000 and newer.
If you use SQL Server 2008 or newer and the DATE datatype (only DATE - not DATETIME!), then you can indeed also use the YYYY-MM-DD format and that will work, too, with any settings in your SQL Server.
Don't ask me why this whole topic is so tricky and somewhat confusing - that's just the way it is. But with the YYYYMMDD format, you should be fine for any version of SQL Server and for any language and dateformat setting in your SQL Server.
The recommendation for SQL Server 2008 and newer is to use DATE if you only need the date portion, and DATETIME2(n) when you need both date and time. You should try to start phasing out the DATETIME datatype if ever possible.
So in your concrete case, try this:
CREATE PROC dbo.WSL_ProjectSearchByDate
#param1 DATETIME2(0) --Search Date
-- #param1 DATETIME2(0) -- or use this, if you really only care about DATE - no time portion
AS
SET NOCOUNT ON;
SELECT
project AS Project,
project_desc AS Description
status_gl AS Status
FROM
dbo.PJPROJ
WHERE
crtd_datetime >= #param1
OR lupd_datetime >= #param1;