SQL - Hours of operation - datetime

Question

I'm having a hard time wrapping my head around what seems to be a somewhat simple issue. Let's say that I have a business whose hours are 12PM - 3AM daily. Each customer gets a bonus once per day based on their initial purchase for that day. So, let's say they spend twenty bucks on their first transaction that day -- they might get a twenty percent discount on that transaction, and that's it for the day.
I'm trying to figure out the most accurate way to check the last bonus that was given and make sure that the customer is eligible for one. I can't do a simple 24-hour check, obviously, because if a customer comes in at 11 PM Monday, for instance, and again at noon Tuesday, they will not get their second bonus.
We are using a VB6 frontend for our POS, with a SQL Server 2008 R2 database. Each time a bonus is applied, it is audited on the database side, so I can easily query the last time the bonus was applied.
EDIT: I should note that, for various reasons, the solution cannot include making any changes to the structure of the database.

Answer 1

I'm not sure on which side (VB or SQL) you want to apply the biz logic but in either case the process should be the same: You need to persist each customer's daily hours of operation with two attributes:
Time (the time of day that they open for business)
TimeSpan (number of hours of operation)
You then check if a transaction's time is between Time and Time + TimeSpan to calculate your business logic and the customer's bonus. Both calculations are fairly trivial in VB and SQL. You just need to make sure you persist the data logically and use it consistently.

Answer 2

I think your answer would be cleaner if you modified it to something like:
IF #LastBonus BETWEEN #store_open AND #store_close
BEGIN
SET #BonusDue = 0
END
ELSE
BEGIN
SET #BonusDue = 1
END
where you figure the store open and close dates based on a fixed times that are added to the date part of the last bonus. Something like
Set #openTime = '12:00'
Convert(date, #LastBonus) + #openTime
And then adding the timespan (as was suggested) to get the close time. It might be a little tricky because if it's after midnight, the open time would need to be added to the previous date instead, but you could probably work this out with a CASE statement. I'd try it out myself if my baby didn't have an ear infection. Hope that is useful to you.

Answer 3

How about:
IF (DATEPART(dayofyear, [lastBonusTime]) <> DATEPART(dayofyear, GetDate())) ...
Where lastBonusTime is the time of the last bonus transaction ?

Answer 4

You can look at the problem a bit differently. If a customer is here now (GETDATE()), has it been over 24 hours since their last purchase?
So, something like
SELECT *
FROM Customers c
INNER JOIN CustomerVisits cv
ON c.CustomerId=cv.CustomerId
INNER JOIN CustomerBonus cb
ON cv.VisitId=cb.VisitId
WHERE c.CustomerId=#CustomerId
AND LastVisitDt BETWEEN
(
DATEADD(hh,12,convert(DATE, LastVisitDt))
)
AND
(
DATEADD(hh,27,convert(DATE, LastVisitDt))
)
AND DATEADD(hh,24,LastVisitDT)<=GETDATE()
I would also consider the specifics of the data--the above is NOT TUNED FOR PERFORMANCE AT ALL. I just wanted to explain my thought process.

Answer 5

In the interest of separating your concerns, I would add a new table, like CUSTOMER_BONUS, with these columns:
BonusStart datetime
BonusEnd datetime
CustomerID int/uniqueidentifier/whatever
TransactionID int/whatever (points to what qualified for the bonus)
When you apply a bonus for a customer for a day, write a new record into this table for the period that it applies to. Presence of a record in this table indicates that the customer is not eligible for another bonus between BonusStart and BonusEnd. When you create a new sale, look in this table. If the record exists, no bonus, but if not, apply the bonus and create a new record here.

Answer 6

I came up with an answer that I'm content with but it's a little kludgy and I would be more than happy to accept a more elegant answer if one is provided. Also, I haven't thoroughly tested this since it's getting late in the day, but if there are flaws in my logic, I will happily revise or accept an answer with revisions.
Basically, I'm just going to determine that the day of the week in terms of a business day is whatever day started four hours ago. This means that all the way up through 3:59 AM, "today" will be considered the day before, which is correct for these hours of operation (I'm overshooting the 3 AM closing time to account for a site deciding to stay open a little later). I then compare this span of time to the most recent time a bonus was applied to that customer's account, using the same rules. If the two match, the bonus has been applied this business day. If they are different, it has not, and the customer is eligible.
DECLARE #CustID AS int
DECLARE #LastBonus AS date
DECLARE #BonusDue AS bit
SET #LastBonus = (SELECT TOP 1 [DateTime] FROM Audit WHERE CustomerID = #CustID AND TransactionType = 'BONUS' ORDER BY [DateTime] DESC)
IF (SELECT DATEADD(hh, -4, CURRENT_TIMESTAMP)) <>
(SELECT DATEADD(hh, -4, #LastBonus))
BEGIN
SET #BonusDue = 1
END
ELSE
BEGIN
SET #BonusDue = 0
END
If I throw this in a stored procedure, I can simply throw a customer ID at it and have it spit out a bit that will show me 1 if the customer is eligible, 0 otherwise. What I don't like about it is that if a customer's hours of operation end up getting much earlier, I'll be sunk (I guess at about 7:00 AM, when simply subtracting four hours will overlap into the previous business day, but subtracting less will not be enough to reach the previous business day). So it will work for the time being, but I'd love to see a better solution.