SQL Segmentation - sql

Question

I have this table
Customer
Amount
Date
Period
Group
77766
50
2022-02-28
1
2
77766
20
2022-03-31
2
2
77766
30
2022-04-30
3
3
12345
50
2022-02-28
1
1
12345
20
2022-03-31
2
2
12345
30
2022-04-30
3
3
and I'm trying to achieve this segmentation model where I assign a Group to its corresponding Period per Customer
Customer
Amount
Date
Period
Group
Group_Period1
Group_Period2
Group_Period3
77766
50
2022-02-28
1
2
2
2
3
77766
20
2022-03-31
2
2
2
2
3
77766
30
2022-04-30
3
3
2
2
3
12345
50
2022-02-28
1
1
1
2
3
12345
20
2022-03-31
2
2
1
2
3
12345
30
2022-04-30
3
3
1
2
3
I tried case function but it didn't work
select a.*,
case when a.Period=1 then Group end Grupo1 ,
case when a.Period=2 then Group2 end Grupo2 ,
case when a.Period=3 then Group3
end Grupo3
from a
I got this output:
Customer
Amount
Date
Period
Group
Group_Period1
Group_Period2
Group_Period3
77766
50
2022-02-28
1
2
2
null
null
77766
20
2022-03-31
2
2
null
2
null
77766
30
2022-04-30
3
3
null
null
3
12345
50
2022-02-28
1
1
1
null
null
12345
20
2022-03-31
2
2
null
2
null
12345
30
2022-04-30
3
3
null
null
3
Can anybody guide me to achieve the expected? Thank you in advice

Answer 1

You can use window function such as MAX() OVER () with conditionals for values of Period column such as
SELECT *,
MAX(CASE WHEN Period=1 THEN `Group` END)
OVER (PARTITION BY Customer) AS Group_Period1,
MAX(CASE WHEN Period=2 THEN `Group` END)
OVER (PARTITION BY Customer) AS Group_Period2,
MAX(CASE WHEN Period=3 THEN `Group` END)
OVER (PARTITION BY Customer) AS Group_Period3
FROM t -- replace with your table's name
where grouping is figured out through use of PARTITION BY clause
Demo

Answer 2

One approach can be via inline sub-query.
select *,
(select group_1 from cust a where a.customer = b.customer and period=1) Group_Period1,
(select group_1 from cust a where a.customer = b.customer and period=2) Group_Period2,
(select group_1 from cust a where a.customer = b.customer and period=3) Group_Period3
from cust b;
Fiddle here