SQL - Find unique min value and associated columns - sql

Question

I have a set of data as below, showing the history of who has done what with a record. The unique identifier for each record is shown in 'ID' and 'Rec No' is the sequential number assigned to each interaction with the record.
ID Rec No Who Type
1 1 Bob New
1 2 Bob Open
1 3 Bob Assign
1 4 Sarah Add
1 5 Bob Add
1 6 Bob Close
2 1 John New
2 2 John Open
2 3 John Assign
2 4 Bob Assign
2 5 Sarah Add
2 6 Sarah Close
3 1 Sarah New
3 2 Sarah Open
3 3 Sarah Assign
3 4 Sarah Close
I need to find all of the 'Assign' operations. However where multiple 'Assign' are in a certain ID, I want to find the first one. I then also want to find the name of the person who did that.
So ultimately from the above date I would like the output to be-
Who Count (assign)
Bob 1
John 1
Sarah 1
The code I have at the moment is-
SELECT IH.WHO, Count(IH.ID)
FROM Table.INCIDENTS_H IH
WHERE (IH.TYPE = Assign)
GROUP BY IH.WHO
But this gives the output as-
Who Count (assign)
Bob 2
John 1
Sarah 1
As it is finding that Bob did an assign on ID 2, Rec No 4.
Any help would be appreciated. I am using MS SQL.

Answer 1

I think something like this is what you are after:
select
who, count(id)
from (
select ID, Who, row_number() over (partition by ID order by Rec) [rownum]
from Table.INCIDENTS_H IH
WHERE (IH.TYPE = Assign)
) a
where rownum = 1
group by who
This should count only the first Assign (ordered by Rec) within each ID group.

Answer 2

This ought to do it:
SELECT IH.WHO, COUNT(IH.ID)
FROM INCIDENTS_H IH
JOIN (
SELECT ID, MIN([Rec No]) [Rec No]
FROM INCIDENTS_H
WHERE ([Type] = 'Assign')
GROUP BY ID
) IH2
ON IH2.ID = IH.ID AND IH2.[Rec No] = IH.[Rec No]
GROUP BY IH.WHO

Answer 3

You can use row_number to accomplish this
WITH INCIDENTS_H as (
SELECT
1 as ID, 1 as RecNo, 'Bob' as Who, 'New' as type
UNION ALL SELECT 1, 2, 'Bob','Open'
UNION ALL SELECT 1, 3, 'Bob','Assign'
UNION ALL SELECT 1, 4, 'Sarah','Add'
UNION ALL SELECT 1, 5, 'Bob','Add'
UNION ALL SELECT 1, 6, 'Bob','Close'
UNION ALL SELECT 2, 1, 'John','New'
UNION ALL SELECT 2, 2, 'John','Open'
UNION ALL SELECT 2, 3, 'John','Assign'
UNION ALL SELECT 2, 4, 'Bob','Assign'
UNION ALL SELECT 2, 5, 'Sarah','Add'
UNION ALL SELECT 2, 6, 'Sarah','Close'
UNION ALL SELECT 3, 1, 'Sarah','New'
UNION ALL SELECT 3, 2, 'Sarah','Open'
UNION ALL SELECT 3, 3, 'Sarah','Assign'
UNION ALL SELECT 3, 4, 'Sarah','Close')
, GetTheMin AS (
SELECT
ROW_NUMBER() over (partition by id order by recno) row,
ID,
RecNo,
Who,
type
FROM
INCIDENTS_H
WHERE
type = 'Assign'
)
SELECT Who,
COUNT(ID)
FROM GetTheMin
WHERE
row = 1
GROUP BY
who
OR you can use CROSS Apply
SELECT
who,
COUNT(id) id
FROM
(SELECT DISTINCT
MinValues.*
FROM
INCIDENTS_H h
CROSS APPLY ( SELECT TOP 1 *
FROM INCIDENTS_H h2
WHERE h.id = h2.id
ORDER BY ID, RecNo asc) MinValues) getTheMin
GROUP BY WHO
Or you can use Min which uses standard SQL John Fisher's answer demonstrates

Answer 4

Here's a view of everything in the table which should match your "first assign" requirement:
select a.*
from Table.INCIDENTS_H a
inner join
(select ID, min([Rec No]) [Rec No] from Table.INCIDENTS_H where Type = 'Assign' group by ID) b
on a.ID = b.ID and a.[Rec No] = b.[Rec No]
Result:
ID Rec No Who Type
1 3 Bob Assign
2 3 John Assign
3 3 Sarah Assign

Answer 5

select * from
(select
id, rec_no, who
from
operation_history
where
type = 'Assign'
order by rec_no asc) table_alias
group by
id
order by id asc
Tested and here are the results:
id rec_no who
1 3 Bob
2 3 John
3 3 Sarah
(Code not specific to SQL Server)

Answer 6

Here is the query with virtual test data that were mentioned in the original post:
with T (ID, RecNo, Who, Type) as
(
select 1, 1, 'Bob', 'New' union all
select 1, 2, 'Bob', 'open' union all
select 1, 3, 'Bob', 'Assign' union all
select 1, 4, 'Sarah', 'Add' union all
select 1, 5, 'Bob', 'Add' union all
select 1, 6, 'Bob', 'Close' union all
select 2, 1, 'John', 'New' union all
select 2, 2, 'John', 'Open' union all
select 2, 3, 'John', 'Assign' union all
select 2, 4, 'Bob', 'Assign' union all
select 2, 5, 'Sarah', 'Add' union all
select 2, 6, 'Sarah', 'Close' union all
select 3, 1, 'Sarah', 'New' union all
select 3, 2, 'Sarah', 'Open' union all
select 3, 3, 'Sarah', 'Assign' union all
select 3, 4, 'Sarah', 'Close'
)
select top 1 with ties *
from T
where Type = 'Assign'
order by row_number() over(partition by ID order by RecNo)
The "select" statement that can be applied to the real situation from the question might look like:
SELECT TOP 1 WITH TIES
IH.ID, IH.[Rec No], IH.WHO, IH.TYPE
FROM Table.INCIDENTS_H IH
WHERE IH.TYPE = 'Assign'
ORDER BY ROW_NUMBER() OVER(PARTITION BY IH.ID ORDER BY IH.[Rec No]);