SQL JOIN - Select 值到非不同行

Question

This is hard to explain, but I'm doing an inner join on 2 tables where the values in the 2nd table are creating new rows instead of adding the values to the same row but adding the values to the columns instead.

So, my results look like this:

 Employee 1 | Supervisor 1
 Employee 1 | Supervisor 2
 Employee 1 | Supervisor 3

What I want the results to look like are like this

Employee 1 | Supervisor 1 | Supervisor 2 | Supervisor 3`

This way I can formulate my WHERE clause to be a bit more specific

This is the query I'm using so far

SELECT HR.EMPLOYEE, HR_SUPERVISOR.Name
FROM data.dbo.HR
INNER JOIN data.dbo.HR_SUPERVISOR
ON HR.ID = hr_supervisor.ID
WHERE HR.EMPLOYEE IN
  (SELECT HR.EMPLOYEE FROM data.dbo.HR GROUP BY HR.EMPLOYEE HAVING COUNT(*) > 1) AND
  HR_SUPERVISOR.Name like '%Test%' 
  GROUP BY HR_SUPERVISOR.name, HR.EMPLOYEE
  ORDER BY HR.EMPLOYEE ASC

Answer 1

If the maximum number of supervisors is small (1-10) you can use the following method:

1. Get the inner join as base data for the final query
2. Generate a row number for the supervisors
3. Make it horizontal with some sub select (which will run fast enough if you pre-filter the baseData query with where clause)

create view vw_Supervisors as
with baseData as 
(
    SELECT 
        HR.id id, 
        ROW_NUMBER() OVER (partition by HR.id order by HR_SUPERVISOR.Name asc) rowNo, 
        HR.EMPLOYEE employee, 
        HR_SUPERVISOR.Name supervisor 
    FROM HR INNER JOIN HR_SUPERVISOR ON HR.ID = hr_supervisor.ID
)
select 
    b.id,
    b.EMPLOYEE, 
    SUPERVISOR1=(select supervisor from baseData b1 where b1.id=b.id and rowNo=1), 
    SUPERVISOR2=(select supervisor from baseData b1 where b1.id=b.id and rowNo=2), 
    SUPERVISOR3=(select supervisor from baseData b1 where b1.id=b.id and rowNo=3),
    SUPERVISOR4=(select supervisor from baseData b1 where b1.id=b.id and rowNo=4),
    SUPERVISOR5=(select supervisor from baseData b1 where b1.id=b.id and rowNo=5)
from baseData b 
group by b.id, b.employee;

In case of many possible cols you should use the XML way to make it horizontal you can find examples for it (rows to cols t-sql) but it takes more effort for the server to run and harder to handle in frontend because of the changing number of columns.