SQL Server 2019

By using db<>fiddle, you agree to license everything you submit by Creative Commons CC0.

create table tblGroup (
  GroupID int not null, 
  GroupName varchar(100),
  constraint PK_GroupID primary key (GroupID)
)
  
create table tblCustomer (
  CustomerID int not null, 
  Name varchar(100), 
  FatherName varchar(100),
  GroupID int not null,
  constraint PK_CustomerID primary key (CustomerID),
  constraint FK_Customer_Group foreign key (GroupID) references tblGroup (GroupID)
  )

insert into tblGroup (GroupID, GroupName) values
(1001, 'Mr. Debashish and Brothers')

insert into tblCustomer (CustomerID, Name, FatherName, GroupID) values
(101555, 'Mr. Debashish', 'Mr. Deb kumar', 1001),
(101556, 'Mr. Nibash', 'Mr. Debashish', 1001),
(101557, 'Nandika Rani', 'Mr. Debashish', 1001)

select * from tblGroup
select * from tblCustomer


GroupID
GroupName


1001
Mr. Debashish and Brothers




CustomerID
Name
FatherName
GroupID


101555
Mr. Debashish
Mr. Deb kumar
1001

101556
Mr. Nibash
Mr. Debashish
1001

101557
Nandika Rani
Mr. Debashish
1001


select c.CustomerID, 
       c.Name,
       g.GroupName
from   tblCustomer c
  inner join tblGroup g on c.GroupID = g.GroupID


CustomerID
Name
GroupName


101555
Mr. Debashish
Mr. Debashish and Brothers

101556
Mr. Nibash
Mr. Debashish and Brothers

101557
Nandika Rani
Mr. Debashish and Brothers


drop table tblCustomer
drop table tblGroup

CustomerID	Name	FatherName	GroupID
101555	Mr. Debashish	Mr. Deb kumar	1001
101556	Mr. Nibash	Mr. Debashish	1001
101557	Nandika Rani	Mr. Debashish	1001

CustomerID	Name	GroupName
101555	Mr. Debashish	Mr. Debashish and Brothers
101556	Mr. Nibash	Mr. Debashish and Brothers
101557	Nandika Rani	Mr. Debashish and Brothers