Get a unique row based on a column item in SQL query - sql

Question

I have a sql query to return IT tickets and their satisfaction scores however because of the way our ticketing system works this sometimes returns 2 rows for a ticket reference - 1 with a "Not Rated" rating and one with the real rating.
My question is, is there a way to get the query to only return a single row for each Ticket Reference and only return the "Not Rated" rating if another rating does not exist. i.e. when there are 2 rows with the same ticket reference and one has a rating of "Excellent" and one has a rating of "Not Rated" that it only returns the row with the "Excellent" rating. Any with only 1 row that is "Not Rated" should be returned.
The query looks like this so far -
SELECT DISTINCT
t.Rating_Date,
t.id AS 'Ticket Reference',
[Rating]
= CASE
When tt.[rating_id] = 20 then 'Poor'
When tt.[rating_id] = 15 then 'Average'
When tt.[rating_id] = 17 then 'Good'
When tt.[rating_id] = 6 then 'Excellent'
else 'Not Rated'
END,
[subject],
[priority],
[status],
uu.name,
[assignee_id],
[Location],
[technology]
FROM
[DB1].[dbo].[table1] t
INNER JOIN [DB1].[dbo].[table2] tt
ON t.id=tt.ticket_id
LEFT JOIN [DB1].[dbo].[table3] uu
ON t.assignee_id=uu.id
WHERE
t.rating_date > '2013-07-01'
AND status = 'closed'
AND location = 'UK'
AND technology <> 'Not Known'
AND group_id = '5678912'
ORDER BY
t-rating_date

Answer 1

I think you can wrap the first query, order it by rating_id (if Not rated value is 0 you should order DESC, if Not rated is the highest you should order ASC) and then select the first record using the TOP function of sql-server.

Answer 2

I suppose that the following logic can be implemented here. Please, be aware of that I am using sample data and in order to implement the solution you should understand the idea.
Let's say we have the following data:
Note: I am using id "0" for "Not Rated" status.
If I have understand your need correctly, the output data should be something like this:
As you can see from the screenshot above, for Tickets with IDs 1 and 4 we have "Not Rated" records, but we are not showing them. The "Not Rated" state is displayed only for Ticket with ID 3.
The solution:
;WITH DataSource AS
(
SELECT ROW_NUMBER() OVER (PARTITION BY [TicketID] ORDER BY [TicketRateID] DESC) AS [RowNumber]
,[TicketID]
,[TicketRateID]
FROM #DataSource
)
SELECT [TicketID]
,[RowNumber]
,[TicketRateID]
FROM DataSource
The SQL statement above is using ROW_NUMBER function in order to create a unique ID for each set of records for given tickets. We are sorting the records with DESC directive in order to be sure the "0"/"Not rated" records will have bigger ID.
The output of previous statement is:
As you can see from the screenshot above, we need to display only this records with RowNumber equal to 1. This is done simple with WHERE clause.
Follows, full working example:
SET NOCOUNT ON
GO
DECLARE #DataSource TABLE
(
[TicketID] TINYINT
,[TicketRateID] TINYINT
)
INSERT INTO #DataSource ([TicketID],[TicketRateID])
VALUES (1,6)
,(1,0)
,(2,20)
,(3,0)
,(4,0)
,(4,15)
;WITH DataSource AS
(
SELECT ROW_NUMBER() OVER (PARTITION BY [TicketID] ORDER BY [TicketRateID] DESC) AS [RowNumber]
,[TicketID]
,[TicketRateID]
FROM #DataSource
)
SELECT [TicketID]
,[RowNumber]
,[TicketRateID]
FROM DataSource
WHERE [RowNumber] = 1
SET NOCOUNT OFF
GO