Date Exists between Range of Dates not working - sql-server

Question

ALTER PROCEDURE [dbo].[spInsert]
(#PlanName Varchar(50)=null
,#StartDate Datetime
,#EndDate Datetime
,#ModifiedBy Varchar(100)=null
,#ReturnValue Int Out)
As
BEGIN
IF NOT EXISTS(SELECT PlanName FROM dbo.tblPlan WHERE PlanName=#PlanName)
BEGIN
IF((SELECT COUNT(*) FROM tblPlan WHERE StartDate <= #StartDate AND EndDate <=
#EndDate)<0)
BEGIN
INSERT INTO dbo.tblPlan VALUES(3,#PlanName,#StartDate,#EndDate,#ModifiedBy,GETDATE(),
(SELECT DATEDIFF(DD,#StartDate,#EndDate)))
SET #ReturnValue=1;
END
ELSE
SET #ReturnValue=-2;
END
ELSE
SET #ReturnValue=-1;
END
I am trying to achieve the below thing.I want to check user supplied startDate and Enddate is in between the existing table startdate and enddate. if any of the date of user supplied date range is in between the tables start date and end date,it should return -2,if the record does not exists it should insert the details..
I Could not achieve this logic.where i went wrong ..please suggest me any solution to this.
EDIT:First Consditon check whether planName is exists or not,If not exists then want to check Start and End Date already existed or Not(Including start and End)
I tried two ways as suggested mentioned in the replies.
eg:If existing start and end range is Start-2013-10-09,End-2013-10-15,If am going to insert another plan then the start and end date of this plan should not fall between 9th-15th october and start and End date should not be 9th or 15 th both.
ONE:IF((SELECT COUNT(*) FROM tblPlan WHERE StartDate <= #StartDate AND EndDate <=
#EndDate)=0)
Result: It does not insert any data, even it is out of previous date. or with in the
range
SECOND:IF((SELECT COUNT(*) FROM tblPlan WHERE StartDate>=#StartDate AND
EndDate<=#EndDate)=0)
RESULT: It insert the date with out Considering the above condition.

Answer 1

I think you need to change your if from
IF((SELECT COUNT(*) FROM tblPlan WHERE StartDate <= #StartDate AND EndDate <= #EndDate)<0)
to
IF((SELECT COUNT(*) FROM tblPlan WHERE StartDate <= #StartDate AND EndDate >= #EndDate)=0)
Which should ensure that #StartDate and #EndDate is between StartDate and EndDate and test for =0

Answer 2

COUNT(*) can never be smaller than zero like your code suggests.
It's either a positive integer (which is greater than zero), or null, which will also return false on any arithmetic condition.

Answer 3

try the below :
ALTER PROCEDURE [dbo].[spInsert]
(#PlanName Varchar(50)=null
,#StartDate Datetime
,#EndDate Datetime
,#ModifiedBy Varchar(100)=null
,#ReturnValue Int Out)
As
BEGIN
IF NOT EXISTS(SELECT PlanName FROM dbo.tblPlan WHERE PlanName=#PlanName)
BEGIN
IF((SELECT COUNT(*) FROM tblPlan WHERE StartDate >= #StartDate AND EndDate <=
#EndDate)=0)
BEGIN INSERT INTO dbo.tblPlan
VALUES(3,#PlanName,#StartDate,#EndDate,#ModifiedBy,GETDATE(),
(SELECT DATEDIFF(DD,#StartDate,#EndDate)))
SET #ReturnValue=1;
END
ELSE
SET #ReturnValue=-2;
END
ELSE
SET #ReturnValue=-1;
END
As count always return positive value or zero. so your first condition always being false.
*UPDATE:*
you want to say if Sdate is '12-12-2013' and edate is '15-12-2013' then you don't want to considers these dates in check if so then try replace the query with below:
IF((SELECT COUNT(*) FROM tblPlan WHERE StartDate > #StartDate AND EndDate <
#EndDate)=0)

Answer 4

If you're wanting to check whether the period defined by #StartDate,#EndDate overlaps with any period defined by the values in the StartDate,EndDate columns for a particular row, then the actual comparison that you want to perform is:
StartDate < #EndDate AND EndDate < #StartDate
(With appropriate adjustments of < to <= depending on whether you want to consider two periods such that one starts at the exact time that the other finishes as overlapping or not)
The logic is - Two periods overlap if both of the following conditions are true:
period 1 starts before period 2 ends
period 2 starts before period 1 ends
Other notes -
A COUNT will never be <0 so that part of the logic is incorrect. If you merely want to determine whether any rows exists, use EXISTS (as you already have once) - don't force a COUNT if you don't actually need to know how many rows match your criteria.
I also find it slightly suspect that your first query considers PlanName but your second doesn't. Are you sure that this is correct?