How to select top record based on the state column

Hi EE,

I have got a sample data as
DECLARE @data TABLE (ContractId INT, WorkorderId INT, AppointmentState VARCHAR(15), DateCreated DATETIME)
INSERT INTO @data VALUES (1,1,'Requested','20180310'),
						 (1,2,'Booked','20180309'),
						 (1,3,'Outstanding','20180308'),
						 (2,1,'Booked','20180310'),
						 (2,2,'Booked','20180309'),
						 (2,2,'Requested','20180308')

select * from @data

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In the dataset against the contractid 1 i have got multiple workorderid. I can have Appointment State of Booked, Requested and Outstanding.
1. If the AppointmentState of any workorder is Booked then i want only that record in my result set.
2. If the appointment status dones't contain Booked but if it contains Requested then i want only that record in my result set
3. If all the records of that contractid dont' have Booked and Requested state then i want to display that record only.
4. If there are duplicate states for a contractid for example two states of Booked then i want to get the first record by date created.

I can do this by WHILE loop but was just wondering is there any other way of doing it as the data set contains over 150,000 records and the performance of while loop will be very slow.

Kindest regards
Ali ShahSQL DeveloperAsked:
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ste5anSenior DeveloperCommented:
If I understand you correctly, then you just need an TOP per GROUP BY, which is easily done with ROWNUMBER(). This is also much faster than a RBAR:

DECLARE @Data TABLE
    (
        ContractId INT ,
        WorkorderId INT ,
        AppointmentState VARCHAR(15) ,
        DateCreated DATETIME
    );

INSERT INTO @Data
VALUES ( 1, 1, 'Requested', '20180310' ) ,
       ( 1, 2, 'Booked', '20180309' ) ,
       ( 1, 3, 'Outstanding', '20180308' ) ,
       ( 2, 1, 'Booked', '20180310' ) ,
       ( 2, 2, 'Booked', '20180309' ) ,
       ( 2, 2, 'Requested', '20180308' ) ,
       ( 3, 2, 'Booked', '20180309' ) ,
       ( 3, 3, 'Outstanding', '20180308' ) ,
       ( 4, 2, 'Requested', '20180308' ) ,
       ( 5, 3, 'Outstanding', '20180308' );

WITH [Data]
AS ( SELECT * ,
            ROW_NUMBER() OVER ( PARTITION BY D.ContractId
                                ORDER BY CASE D.AppointmentState
                                              WHEN 'Booked' THEN 1
                                              WHEN 'Requested' THEN 2
                                              WHEN 'Outstanding' THEN 3
                                              ELSE 999
                                         END ,
                                         D.DateCreated ASC ) AS RN
     FROM   @Data D )
SELECT *
FROM   [Data] D
WHERE  D.RN = 1;

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Ali ShahSQL DeveloperAuthor Commented:
That is brilliant. Yes that's what i wanted. Thanks a lot
you are a star
Regards,
0
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