SQL Apply Distinct One Column [duplicate] - sql

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Get top 1 row of each group
(19 answers)
Closed 9 months ago.
I have a SQL query as below. I want to apply DISTINCT to Name column in this query. Can you help me?
SELECT Id,
ConflictCheckRequestIndividualId,
Name,
Surname,
it.IndividualType AS IndividualType,
JobTitle,
RegistrationNumber,
Title,
District,
Status,
CreatedBy,
Created,
ModifiedBy,
Modified
FROM ConflictCheckItoIndividual
LEFT JOIN #IndividualTypes it
ON it.IndividualId = ConflictCheckRequestIndividualId
WHERE ConflictCheckRequestIndividualId IN
(SELECT Id
FROM ConflictCheckRequestIndividual
WHERE ConflictCheckRequestId = #ConflictId
AND SubStatus = 2)

Answer 1

Two ways with subtly different results. "GROUP BY X" is another way of saying "Give me one row per X". You will have to apply an aggregation function to each other row so it knows how to squash the rows into 1:
SELECT MAX(Id),
MAX(ConflictCheckRequestIndividualId),
Name,
MAX(Surname),
MAX(it.IndividualType) AS IndividualType,
MAX(JobTitle),
MAX(RegistrationNumber),
MAX(Title),
MAX(District),
MAX(Status),
MAX(CreatedBy),
MAX(Created),
MAX(ModifiedBy),
MAX(Modified)
FROM ConflictCheckItoIndividual
LEFT JOIN #IndividualTypes it
ON it.IndividualId = ConflictCheckRequestIndividualId
WHERE ConflictCheckRequestIndividualId IN
(SELECT Id
FROM ConflictCheckRequestIndividual
WHERE ConflictCheckRequestId = #ConflictId
AND SubStatus = 2)
GROUP BY Name
This might end up with data for each field coming from different rows. If you wanted all data to come from one row, you could do this
;WITH cte AS
(
SELECT Id,
ConflictCheckRequestIndividualId,
Name,
Surname,
it.IndividualType AS IndividualType,
JobTitle,
RegistrationNumber,
Title,
District,
Status,
CreatedBy,
Created,
ModifiedBy,
Modified,
ROW_NUMBER() OVER (PARTITION BY Name ORDER BY Modified DESC) as rownum
FROM ConflictCheckItoIndividual
LEFT JOIN #IndividualTypes it
ON it.IndividualId = ConflictCheckRequestIndividualId
WHERE ConflictCheckRequestIndividualId IN
(SELECT Id
FROM ConflictCheckRequestIndividual
WHERE ConflictCheckRequestId = #ConflictId
AND SubStatus = 2)
)
SELECT * FROM cte WHERE rownum = 1
This is "Partitioning" the data into one bucket per Name. Within each bucket, its ordering the rows by Modified in descending order. We then only pick out one row from each bucket - the most recently Modified one.
As an aside, given that there is a Name and a Surname field, I would expect to group by that as well

Answer 2

Just realize that what your asking for means: You get a random dataset for 1 particular Name, but if that's good enough for you at this moment this code should do:
select * from (
SELECT
ROW_NUMBER() over (partition by Name order by Id) [row],
Id,
ConflictCheckRequestIndividualId,
Name,
Surname,
it.IndividualType AS IndividualType,
JobTitle,
RegistrationNumber,
Title,
District,
Status,
CreatedBy,
Created,
ModifiedBy,
Modified
FROM ConflictCheckItoIndividual
LEFT JOIN #IndividualTypes it
ON it.IndividualId = ConflictCheckRequestIndividualId
WHERE ConflictCheckRequestIndividualId IN
(SELECT Id
FROM ConflictCheckRequestIndividual
WHERE ConflictCheckRequestId = #ConflictId
AND SubStatus = 2)) data
where [row] = 1
Will you let me know if this works for you?