Query for one row of each distinct column value

Question

lets say theres table employee with columns name, id, and title. How do you get one row for each distinct title. Whatever row it is doesnt matter as long as your result set covers every possible employee title. How can I do this? thanks

Answer 1

Hi,
I think you're asking about a Top-N Query .
Since you didn't post a version of your table, I'll use scott.emp to illustrate.
The following query shows exactly one row of output for each distinct job:
WITH        got_r_num         AS
     SELECT     empno, ename, job
     ,     ROW_NUMBER () OVER ( PARTITION BY  job
                               ORDER BY          ename
                             ) AS r_num
     FROM    scott.emp
SELECT     empno, ename, job
FROM     got_r_num
WHERE     r_num     = 1
;Output:
`    EMPNO ENAME      JOB
      7902 FORD       ANALYST
      7876 ADAMS      CLERK
      7698 BLAKE      MANAGER
      7839 KING       PRESIDENT
      7499 ALLEN      SALESMANThe rows you see are actual rows from the table, not aggregates. That is, you can be certain that there is a row in the table with empno=7902, ename='FORD' and job='ANALYST'.
I hope this answers your question.
If not, post a little sample data (CREATE TABLE and INSERT statements, relevant columns only), and also post the results you want from that data.
If the desired results are not unique, that is, if you'd be equally satisfied with a number of different result sets, then post a couple of examples from the same sample data.