SQL Server 2019

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create table parenttable
(
  id int identity,
  Name nvarchar(10),
  primary key(id)
)

create table childtable
(
  id int identity,
  parent_id int,
  attribute nvarchar(50),
  valueattribute nvarchar(50),
  date_time datetime,
  primary key(id),
  foreign key(parent_id)references parenttable
);
insert into parenttable values
('P1'),
('P2')

insert into childtable values
(1,'attribute1','A','2021-01-01 00:00:00'),
(1,'attribute2','20','2021-01-01 00:00:00'),
(1,'attribute1','B','2021-01-01 00:00:00'),
(1,'attribute2','10','2021-01-01 00:00:00'),
(1,'attribute3','200','2021-01-01 00:00:00'),
(1,'attribute4','300','2021-01-01 00:00:00'),
(2,'attribute1','C','2021-01-01 00:00:00'),
(2,'attribute2','25','2021-01-01 00:00:00'),
(2,'attribute3','150','2021-01-01 00:00:00'),
(2,'attribute4','400','2021-01-01 00:00:00')
12 rows affected

select *
from parenttable p join childtable c on p.id = c.parent_id


id
Name
id
parent_id
attribute
valueattribute
date_time


1
P1
1
1
attribute1
A
2021-01-01 00:00:00.000

1
P1
2
1
attribute2
20
2021-01-01 00:00:00.000

1
P1
3
1
attribute1
B
2021-01-01 00:00:00.000

1
P1
4
1
attribute2
10
2021-01-01 00:00:00.000

1
P1
5
1
attribute3
200
2021-01-01 00:00:00.000

1
P1
6
1
attribute4
300
2021-01-01 00:00:00.000

2
P2
7
2
attribute1
C
2021-01-01 00:00:00.000

2
P2
8
2
attribute2
25
2021-01-01 00:00:00.000

2
P2
9
2
attribute3
150
2021-01-01 00:00:00.000

2
P2
10
2
attribute4
400
2021-01-01 00:00:00.000

id	Name	id	parent_id	attribute	valueattribute	date_time
1	P1	1	1	attribute1	A	2021-01-01 00:00:00.000
1	P1	2	1	attribute2	20	2021-01-01 00:00:00.000
1	P1	3	1	attribute1	B	2021-01-01 00:00:00.000
1	P1	4	1	attribute2	10	2021-01-01 00:00:00.000
1	P1	5	1	attribute3	200	2021-01-01 00:00:00.000
1	P1	6	1	attribute4	300	2021-01-01 00:00:00.000
2	P2	7	2	attribute1	C	2021-01-01 00:00:00.000
2	P2	8	2	attribute2	25	2021-01-01 00:00:00.000
2	P2	9	2	attribute3	150	2021-01-01 00:00:00.000
2	P2	10	2	attribute4	400	2021-01-01 00:00:00.000