How to pass optional date parameters in SQL Server - sql-server

Question

I think this should be simple, but I keep running into problems.
I simply want to return all data from a table that lies between a date range. But I want the date range to be optional.
ALTER PROCEDURE [dbo].[sp_ExistingPlacements_Get]
#DateFrom DATE = NULL,
#DateTo DATE = NULL
AS
BEGIN
SET NOCOUNT ON;
SELECT *
FROM tblExistingPlacements
WHERE
CreatedDT > COALESCE(NULLIF(#DateFrom, ''), #DateFrom)
AND
CreatedDT < COALESCE(NULLIF(#DateTo, GETDATE()), #DateTo)
END
So, if no dates are passed in, we return the entire table.
If only the start date (DateFrom) is passed, we return rows > the start date and all the up to the current date.
If only the End date (DateTo) is passed then return all the rows < the End Date
And of course if both dates are passed, return all the rows inbetween those dates.
Am I going the wrong route with COALESCE ?

Answer 1

Use ISNULL(#parameter) OR (--your condition--) instead of COALESCE:
BEGIN
SET NOCOUNT ON;
SELECT *
FROM tblExistingPlacements
WHERE
((#DateFrom IS NULL) OR CreatedDT > #DateFrom)
AND
((#DateTo IS NULL) OR CreatedDT < #DateTo)
END
If parameter was not provided ISNULL return TRUE, so second part of OR won't matter.

Answer 2

Do not do this. SQL will have to create one execution plan that works in any situation. As unituitive as it sounds, is better to have three separate queries:
ALTER PROCEDURE [dbo].[sp_ExistingPlacements_Get]
#DateFrom DATE = NULL,
#DateTo DATE = NULL
AS
BEGIN
SET NOCOUNT ON;
IF (#DateFrom IS NULL and #DateTo IS NULL)
SELECT field, field, field
FROM tblExistingPlacements
WHERE CreatedDT < GETUTCDATE();
ELSE IF (#DateFrom IS NULL)
SELECT field, field, field
FROM tblExistingPlacements
WHERE CreatedDT < #dateTo;
ELSE IF (#DateTo IS NULL)
SELECT field, field, field
FROM tblExistingPlacements
WHERE CreatedDT BETWEEN #DateFrom AND GETUTCDATE();
ELSE
SELECT field, field, field
FROM tblExistingPlacements
WHERE CreatedDT BETWEEN #DateFrom AND #DateTo;
END
The wisdom of returning the entire table when no parameters are specified is highly questionable, but that is not the point. Besides:
never use * in queries, always specify the projection list explicitly
always use UTC times in the database
For a thorough discussion of this topic see Dynamic Search Conditions in T-SQL.