Min() and Max() based on partition in sql server

Question

I want to use min & max function but on certain criteria.

Create Table #Test (Id Int Identity(1,1), Category Varchar(100), DateTimeStamp DateTime)



    Insert into #Test (Category,DateTimeStamp) values ('c1','2019-08-13 01:00:13.503')
        Insert into #Test (Category,DateTimeStamp) values ('c1','2019-08-13 02:00:13.503')
        Insert into #Test (Category,DateTimeStamp) values ('c1','2019-08-13 03:00:13.503')
        Insert into #Test (Category,DateTimeStamp) values ('c1','2019-08-13 04:00:13.503')
        Insert into #Test (Category,DateTimeStamp) values ('c1','2019-08-13 05:00:13.503')
        Insert into #Test (Category,DateTimeStamp) values ('c2','2019-08-13 06:00:13.503')
        Insert into #Test (Category,DateTimeStamp) values ('c2','2019-08-13 07:00:13.503')
        Insert into #Test (Category,DateTimeStamp) values ('c2','2019-08-13 08:00:13.503')
        Insert into #Test (Category,DateTimeStamp) values ('c2','2019-08-13 09:00:13.503')
        Insert into #Test (Category,DateTimeStamp) values ('c2','2019-08-13 10:00:13.503')  
        Insert into #Test (Category,DateTimeStamp) values ('c1','2019-08-13 11:00:13.503')

Current Query With Output

select category, min(DateTimeStamp) as minn , max(DateTimeStamp) as maxx from #Test
group by category

Current Output

Expected Output

Most people here want sample table data and expected result as formatted text, not as images. — jarlh, Aug 19 '19 at 12:06
I have also shared sample sql data script and current sql query. — Hardik Parmar, Aug 19 '19 at 12:08

score 8 · Accepted Answer · answered Aug 19 '19 at 12:11

You can try below - it's a gap & island problem

DEMO

select category, min(datetimestamp),max(datetimestamp)
from
(
select *,row_number() over(order by datetimestamp) -
row_number() over(partition by category order by datetimestamp) as rn2
from #Test
)A group by category,rn2 order by 2

OUTPUT:

category       minval               maxval
c1             13/08/2019 01:00:13  13/08/2019 05:00:13
c2             13/08/2019 06:00:13  13/08/2019 10:00:13
c1             13/08/2019 11:00:13  13/08/2019 11:00:13

score 1 · Answer 2 · edited Aug 19 '19 at 12:56

1

For postgres:

SELECT category, min(DateTimeStamp) as minn , max(DateTimeStamp) as maxx 
FROM (Select *,
      SUM(CASE WHEN Category <> PrevCategory THEN 1 ELSE 0 END)  OVER (ORDER BY 
      ID,Category,DateTimeStamp) As partition
      From (Select * ,LAG (Category, 1) OVER (ORDER BY ID) AS PrevCategory From Test)  As 
           help) As helper 
GROUP BY category,partition;

edited Aug 19 '19 at 12:56

Alfonso Tienda

3,442
1
19
34

answered Aug 19 '19 at 12:54

Martin Stagl

56
3

Min() and Max() based on partition in sql server

2 Answers2

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