SQL query - return single unique rows

Question

Hi
If you have an employee table where employees are listed per department, using SQL, how could you return the names of the employees listed per department on a single unique row?
Eg - select deptno, first_name from employee
deptno first_name
10 Jane
20 Jack
10 Joe
20 Jill
10 Jacinta
30 John
30 Jeffrey
10 Jackie
30 Jennifer
... etc.
the return set of the query would look like:
deptno first_name concat
10 Jane Joe Jacinta Jackie ..
20 Jack Jill ..
30 John Jeffrey Jennifer ..
Cheers

Answer 1

Here you go:
WITH t AS
(SELECT 10 deptno, 'Jane' first_name FROM dual UNION
SELECT 20 deptno, 'Jack' first_name FROM dual UNION
SELECT 10 deptno, 'Joe' first_name FROM dual UNION
SELECT 20 deptno, 'Jill' first_name FROM dual UNION
SELECT 10 deptno, 'Jacinta' first_name FROM dual UNION
SELECT 30 deptno, 'John' first_name FROM dual UNION
SELECT 30 deptno, 'Jeffrey' first_name FROM dual UNION
SELECT 10 deptno, 'Jackie' first_name FROM dual UNION
SELECT 30 deptno, 'Jennifer' first_name FROM dual)
SELECT   deptno,
         RTRIM(XMLAGG(XMLELEMENT(c, first_name||' ') ).EXTRACT ('//text()'), ' ') names
FROM     t
GROUP BY deptno