SQL Find latest record only if COMPLETE field is 0 - sql

Question

I have a table with multiple records submitted by a user. In each record is a field called COMPLETE to indicate if a record is fully completed or not.
I need a way to get the latest records of the user where COMPLETE is 0, LOCATION, DATE are the same and no additional record exist where COMPLETE is 1. In each record there are additional fields such as Type, AMOUNT, Total, etc. These can be different, even though the USER, LOCATION, and DATE are the same.
There is a SUB_DATE field and ID field that denote the day the submission was made and auto incremented ID number. Here is the table:
ID NAME LOCATION DATE COMPLETE SUB_DATE TYPE1 AMOUNT1 TYPE2 AMOUNT2 TOTAL
1 user1 loc1 2017-09-15 1 2017-09-10 Food 12.25 Hotel 65.54 77.79
2 user1 loc1 2017-09-15 0 2017-09-11 Food 12.25 NULL 0 12.25
3 user1 loc2 2017-08-13 0 2017-09-05 Flight 140 Food 5 145.00
4 user1 loc2 2017-08-13 0 2017-09-10 Flight 140 NULL 0 140
5 user1 loc3 2017-07-14 0 2017-07-15 Taxi 25 NULL 0 25
6 user1 loc3 2017-08-25 1 2017-08-26 Food 45 NULL 0 45
The results I would like is to retrieve are ID 4, because the SUB_DATE is later that ID 3. Which it has the same Name, Location, and Date information and there is no COMPLETE with a 1 value.
I would also like to retrieve ID 5, since it is the latest record for the User, Location, Date, and Complete is 0.
I would also appreciate it if you could explain your answer to help me understand what is happening in the solution.

Answer 1

Not sure if I fully understood but try this
SELECT *
FROM (
SELECT *,
MAX(CONVERT(INT,COMPLETE)) OVER (PARTITION BY NAME,LOCATION,DATE) AS CompleteForNameLocationAndDate,
MAX(SUB_DATE) OVER (PARTITION BY NAME, LOCATION, DATE) AS LastSubDate
FROM your_table t
) a
WHERE CompleteForNameLocationAndDate = 0 AND
SUB_DATE = LastSubDate
So what we have done here:
First, if you run just the inner query in Management Studio, you will see what that does:
The first max function will partition the data in the table by each unique Name,Location,Date set.
In the case of your data, ID 1 & 2 are the first partition, 3&4 are the second partition, 5 is the 3rd partition and 6 is the 4th partition.
So for each of these partitions it will get the max value in the complete column. Therefore any partition with a 1 as it's max value has been completed.
Note also, the convert function. This is because COMPLETE is of datatype BIT (1 or 0) and the max function does not work with that datatype. We therefore convert to INT. If your COMPLETE column is type INT, you can take the convert out.
The second max function partitions by unique Name, Location and Date again but we are getting the max_sub date this time which give us the date of the latest record for the Name,Location,Date
So we take that query and add it to a derived table which for simplicity we call a. We need to do this because SQL Server doesn't allowed windowed functions in the WHERE clause of queries. A windowed function is one that makes use of the OVER keyword as we have done. In an ideal world, SQL would let us do
SELECT *,
MAX(CONVERT(INT,COMPLETE)) OVER (PARTITION BY NAME,LOCATION,DATE) AS CompleteForNameLocationAndDate,
MAX(SUB_DATE) OVER (PARTITION BY NAME, LOCATION, DATE) AS LastSubDate
FROM your)table t
WHERE MAX(CONVERT(INT,COMPLETE)) OVER (PARTITION BY NAME,LOCATION,DATE) = 0 AND
SUB_DATE = MAX(SUB_DATE) OVER (PARTITION BY NAME, LOCATION, DATE)
But it doesn't allow it so we have to use the derived table.
So then we basically SELECT everything from our derived table Where
CompleteForNameLocationAndDate = 0
Which are Name,Location, Date partitions which do not have a record marked as complete.
Then we filter further asking for only the latest record for each partition
SUB_DATE = LastSubDate
Hope that makes sense, not sure what level of detail you need?
As a side, I would look at restructuring your tables (unless of course you have simplified to better explain this problem) as follows:
(Assuming the table in your examples is called Booking)
tblBooking
BookingID
PersonID
LocationID
Date
Complete
SubDate
tblPerson
PersonID
PersonName
tblLocation
LocationID
LocationName
tblType
TypeID
TypeName
tblBookingType
BookingTypeID
BookingID
TypeID
Amount
This way if you ever want to add Type3 or Type4 to your booking information, you don't need to alter your table layout