n to n relationship how to obtain a result in one row - sql

Question

so I have an employee that can work in many companies so I have an n to n relationship, how can I obtain the companies that one employee works in, in just one row with sql?
example
table - employee
Employeeid employeename
1 mike
table company
companyId CompanyName
1 cocacola
2 nokia
3 intel
table employeeCompany
id employeeid companyid
1 1 1
2 1 2
3 1 3
I thought with this but can´t
select Employeeid , companyid
from employeeCompany
where employeeid = 1
group by Employeeid , companyid

Answer 1

Easiest way to do it in Sql Server is by use of FOR XML PATH. The cryptic part .value('text()[1]','nvarchar(max)') handles special xml characters.
select employee.*, companies.*
from Employee
OUTER APPLY
(
select stuff ((SELECT ', ' + Company.CompanyName
FROM EmployeeCompany
INNER JOIN Company
ON EmployeeCompany.CompanyId = Company.CompanyID
WHERE EmployeeCompany.employeeid = Employee.EmployeeID
ORDER BY Company.CompanyName
FOR XML PATH(''),TYPE).value('text()[1]','nvarchar(max)')
, 1, 2, '') Companies
) companies
See demo at Sql Fiddle.

Answer 2

It sounds like you want something that is similar to mySQL's Group_Concat in SQL Server?
If you are looking for a way to do this so that each companyid is in a separate column, then that would only be possible with some difficulty using dynamic SQL. At which time it might be easier to just return this to an application and let it handle what it needs within its own logic?
BTW, the dynamic SQL logic would go something like this in case you were wondering...notice how nasty it is...thus why I would suggest against it.
select #highestCount = max(count(*))
from employeeCompany
group by Employeeid
declare createtemptable varchar(max), #filltableselect varchar(max), #filltablejoin varchar(max)
declare #currentCount int
set #currentCount = 0
set #createtemptable = 'CREATE TABLE #Temp (EmployeeID INT'
set #filltableselect = 'INSERT INTO #Temp SELECT EmployeeCompany0.EmployeeID, EmployeeCompany0.CompanyID'
set #filltablejoin = 'FROM EmployeeCompany AS EmployeeCompany0'
while(#currentCount < #highestCount)
begin
set #createtemptable = #createtemptable + ', CompanyID'
+ CAST(#currentCount AS VARCHAR(2)) + ' INT'
if(#currentCount > 0)
begin
set #filltableselect = #filltableselect + ', EmployeeCompany'
+ CAST(#currentCount AS VARCHAR(2)) + '.CompanyId'
set #filltablejoin = #filltablejoin
+ 'LEFT JOIN EmployeeCompany AS EmployeeCompany'
+ CAST(#currentCount AS VARCHAR(2))
+ ' ON EmployeeCompany0.EmployeeID = EmployeeCompany'
+ CAST(#currentCount AS VARCHAR(2)) + '.EmployeeID'
end
set #currentCount = #currentCount + 1
end
set #createtemptable = #createtemptable + ')'
--This next line can be whatever you need it to be
set #filltablejoin = #filltablejoin + 'WHERE employeeCompany0.EmployeeID = 1'
exec #createtemptable
exec #filltableselect + #filltablejoin