How to do pivoting on this layered data - sql

Question

Hi I have sample data
declare #emp table(id int identity(1,1),E_Name varchar(20),E_company varchar(20),Emp_Val VARCHAR(10))
insert into #emp(E_Name,E_company,Emp_Val)VALUES('Rahim','WELLS','A')
insert into #emp(E_Name,E_company,Emp_Val)VALUES('Jag','collebra',NULL)
insert into #emp(E_Name,E_company,Emp_Val)VALUES('Vasu','nunet',NULL)
insert into #emp(E_Name,E_company,Emp_Val)VALUES('Kiran','crystal',NULL)
insert into #emp(E_Name,E_company,Emp_Val)VALUES('Sajan','tiato',NULL)
insert into #emp(E_Name,E_company,Emp_Val)VALUES('RAM','WELLS','A')
insert into #emp(E_Name,E_company,Emp_Val)VALUES('Srinu','Cognizant','B')
insert into #emp(E_Name,E_company,Emp_Val)VALUES('Raju','Cognizant','B')
Sample data :
id E_Name E_company Emp_Val
1 Rahim WELLS A
2 Jag collebra NULL
3 Vasu nunet NULL
4 Kiran crystal NULL
5 Sajan tiato NULL
6 RAM WELLS A
7 Srinu Cognizant B
8 Raju Cognizant B
script :
SELECT [WELLS],[Cognizant],[NULL] from (
select E_Name,E_company,Emp_Val from #emp)T
PIVOT (MAX(E_Name)FOR E_company IN([WELLS],[Cognizant],[NULL]))PVT
output :
WELLS Cognizant NULL
Rahim Srinu collebra
RAM Raju tiato
NULL Srinu crystal
NULL NULL NUNET

Answer 1

You can use conditional aggregation:
select max(case when e_company = 'WELLS' then e_name end) as wells,
max(case when e_company = 'Cognizant' then e_name end) as cognizant,
max(case when e_company not in ('WELLS', 'Cognizant') then e_name end) as nulls
from (select e.*,
row_number() over (partition by (case when e_company in ('WELLS', 'Cognizant') then e_company end) order by id) as seqnum
from #emp e
) e
group by seqnum
order by seqnum;
Here is a db<>fiddle.

Answer 2

your mistake is in the last select statement, it should be like this:
SELECT *
from (
select * from #emp)T
PIVOT (MAX(Emp_Val)FOR E_company IN([WELLS],[Cognizant],[NULL]))PVT
order by 1

Answer 3

This approach uses a self join within the pivot to enumerate the companies with multiple employes and values. It then uses a right join back on to the table to enumerate the companies that do not have those employees. The difference in the output is that all of the null permutations are preserved. Other than that this should cover what you are looking for.
declare #emp table(id int identity(1,1),E_Name varchar(20),E_company
varchar(20),Emp_Val VARCHAR(10))
insert into #emp(E_Name,E_company,Emp_Val)VALUES('Rahim','WELLS','A')
insert into #emp(E_Name,E_company,Emp_Val)VALUES('Jag','collebra',NULL)
insert into #emp(E_Name,E_company,Emp_Val)VALUES('Vasu','nunet',NULL)
insert into #emp(E_Name,E_company,Emp_Val)VALUES('Kiran','crystal',NULL)
insert into #emp(E_Name,E_company,Emp_Val)VALUES('Sajan','tiato',NULL)
insert into #emp(E_Name,E_company,Emp_Val)VALUES('RAM','WELLS','A')
insert into #emp(E_Name,E_company,Emp_Val)VALUES('Srinu','Cognizant','B')
insert into #emp(E_Name,E_company,Emp_Val)VALUES('Raju','Cognizant','B')
select distinct WELLS, Cognizant,case E_Company when 'Wells' then NULL when
'Cognizant' then null else E_Company end as [NULL] from
(
SELECT [WELLS],[Cognizant],[collebra], [nunet], [crystal], [tiato] from (
select e.E_Name,e2.E_name as E2_Name, e.E_company,e2.Emp_Val as Emp2_Val, e.Emp_Val
from #emp e inner join #emp e2 on e.id=e2.id)T
PIVOT (MAX(E_Name)FOR E_company IN([WELLS],[Cognizant],[collebra], [nunet],
[crystal], [tiato]))PVT) stagingtable
right join (select E_Company, E_Name from #emp) c on stagingtable.Cognizant=c.E_Name
or stagingtable.WELLS=c.E_Name
order by 1 desc, 2 desc, 3 desc;