Question

I have a sql query that I can not get to work correctly

Here is a simplified version of the query.

select * from Permit 
inner join BMP on Permit.PermitNumber = BMP.PermitNumber
left join BMPInspection as BI on Permit.PermitNumber = BI.PermitNumber and BMP.BMPNumber = BI.BMPNumber

where Permit.PermitNumber = 'S002552' 
AND ( ( @StartDate IS NULL
             AND @EndDate IS NULL )
            OR ( BI.dtActionDate > Dateadd(day, -1, @StartDate)
                 AND BI.dtActionDate < Dateadd(day, 1, @EndDate) )
            OR ( BI.dtActionDate > Dateadd(day, -1, @StartDate)
                 AND @EndDate IS NULL )
            OR ( @StartDate IS NULL
                 AND BI.dtActionDate < Dateadd(day, 1, @EndDate) ) )

The desired behavior is

1. Return only records in the date range when start date and end date are specified
2. Return NULL dates or less than end date when start date is NULL and end date has a date
3. Return NULL or Greater than start date when start date has a date and end date is null
4. Return only records with a NULL date when both start date and end date are NULL

Right now all I can get is is the date range or all records NULLS and valid dates.

Answer 1

For this condition:

Return only records with a NULL date when both start date and end date
are NULL

Change:

( @StartDate IS NULL AND @EndDate IS NULL )

to

( @StartDate IS NULL AND @EndDate IS NULL AND BI.dtActionDate IS NULL)