SQL Query group by in case statement - sql

Question

I Have three tables like bellow
**tRole**
+--------+----------+-----------+
| RoleID | RoleCode | RoleTitle |
+--------+----------+-----------+
| 1 | Role1 | RT1 |
| 2 | Role2 | RT2 |
| 3 | Role3 | RT3 |
+--------+----------+-----------+
**tEmployee**
+-------+-------+
| EmpID | Name |
+-------+-------+
| 1 | Emp 1 |
| 2 | Emp 2 |
| 3 | Emp 3 |
+-------+-------+
**tEmployeeRole**
+-------+--------+
| EmpID | RoleID |
+-------+--------+
| 1 | 1 |
| 1 | 2 |
| 2 | 1 |
| 2 | 2 |
| 3 | 3 |
+-------+--------+
I want a output like below ,If a role mapped with only one employee then employee name will show other wise Multiple will show.
+--------+----------+-----------+----------+
| RoleID | RoleCode | RoleTitle | Employee |
+--------+----------+-----------+----------+
| 1 | Role1 | RT1 | Multiple |
| 2 | Role2 | RT2 | Multiple |
| 3 | Role3 | RT3 | Emp 3 |
+--------+----------+-----------+----------+
I write bellow query but when I group by emp.First_Name then the result is wrong
select cr.RoleCode,cr.RoleID,
case
when count(ear.RoleID)=1 then emp.First_Name
else 'M' end as 'AssignedTO'
from tRole as cr
left outer join tEmployeeRole as ear on cr.RoleID=ear.RoleID
left outer join tEmployee as emp on ear.EmployeeID=emp.EmployeeID
group by cr.RoleCode,crRoleID,emp.First_Name

Answer 1

Hello You can use this query for your solution :
you need to count with partition and use distinct data
DECLARE #tRole TABLE (
RoleID INT
,RoleCode VARCHAR(50)
,RoleTitle VARCHAR(50)
)
DECLARE #tEmployee TABLE (
EmpID INT
,EmpName VARCHAR(50)
)
DECLARE #tEmployeeRole TABLE ( EmpID INT, RoleID INT )
INSERT #tRole ( RoleID, RoleCode, RoleTitle )
SELECT 1, 'Role1', 'RT1'
UNION
SELECT 2, 'Role2', 'RT2'
UNION
SELECT 3, 'Role3', 'RT3'
INSERT #tEmployee ( EmpID, EmpName )
SELECT 1, 'Epm 1'
UNION
SELECT 2, 'Epm 2'
UNION
SELECT 3, 'Epm 3'
INSERT #tEmployeeRole ( EmpID, RoleID )
SELECT 1, 1
UNION
SELECT 1, 2
UNION
SELECT 2, 1
UNION
SELECT 2, 2
UNION
SELECT 3, 3
SELECT DISTINCT tRole.RoleID
, RoleCode
, RoleTitle
, CASE WHEN COUNT(tEmployeeRole.EmpID) OVER ( PARTITION BY tEmployee.EmpID ) = 1 THEN tEmployee.EmpName ELSE 'Multiple'END [Employee]
FROM #tEmployee tEmployee
LEFT OUTER JOIN #tEmployeeRole tEmployeeRole ON tEmployeeRole.EmpID = tEmployee.EmpID
LEFT OUTER JOIN #tRole tRole ON tRole.RoleID = tEmployeeRole.RoleID

Answer 2

You can Modify the answer from #Pratik to add a col that lists the employees
;with CTE as(
SELECT
DISTINCT tRole.RoleID
RoleCode
, RoleTitle
, CASE WHEN COUNT(tEmployeeRole.EmpID) OVER ( PARTITION BY tEmployee.EmpID ) = 1 THEN tEmployee.EmpName ELSE 'Multiple'END [Employee]
FROM #tEmployee tEmployee
LEFT OUTER JOIN #tEmployeeRole tEmployeeRole ON tEmployeeRole.EmpID = tEmployee.EmpID
LEFT OUTER JOIN #tRole tRole ON tRole.RoleID = tEmployeeRole.RoleID
)
select *
,stuff( (select ','+EmpName from #tEmployee IE inner join #tEmployeeRole IER on IE.EmpID = IER.EmpID where IER.RoleID = CTE.rolecode for xml PATH('') ),1,1,'') AS EMList
from CTE

Answer 3

This query might help you out . Make a try
Your Tables Data looks like
create TABLE #tRole (RoleID INT ,RoleCode VARCHAR(50) ,RoleTitle VARCHAR(50) )
create TABLE #tEmployee (EmpID INT ,EmpName VARCHAR(50) )
create TABLE #tEmployeeRole( EmpID INT, RoleID INT )
INSERT #tRole ( RoleID, RoleCode, RoleTitle )
SELECT 1, 'Role1', 'RT1'
UNION
SELECT 2, 'Role2', 'RT2'
UNION
SELECT 3, 'Role3', 'RT3'
INSERT #tEmployee ( EmpID, EmpName )
SELECT 1, 'Epm 1'
UNION
SELECT 2, 'Epm 2'
UNION
SELECT 3, 'Epm 3'
INSERT #tEmployeeRole ( EmpID, RoleID )
SELECT 1, 1
UNION
SELECT 1, 2
UNION
SELECT 2, 1
UNION
SELECT 2, 2
UNION
SELECT 3, 3
Desired Query
;with cte as
(
select tr.roleid,tr.rolecode,tr.roletitle,te.empname
,COUNT(ter.EmpID) OVER ( PARTITION BY ter.EmpID ) as emp_count
from #tEmployee te
inner join #tEmployeeRole tER on tER.empid=te.empid
inner join #tRole tr on tr.roleid=ter.roleid
)
select distinct RoleID,RoleCode,RoleTitle
,case when emp_count>1 then 'Multiple' else empname end as Employee
from cte