14 May, 2015

Display Detail Rows as One Column in Master

Sometimes, it is required to display detail rows as a single column in master row.
For example in scott schema you have two tables ( DEPT, EMP) which relation is 1-M .

If required to display Employees names separated by comma  as one column per every DEPTNO, ÷In order to the final output like the following.

The easiest way to get output of previous diagram is the following SQL query.

    SELECT d.deptNo,
           MAX (SUBSTR (SYS_CONNECT_BY_PATH (d.eName, ','), 2)) employees
      FROM (SELECT deptNo,
                   ROW_NUMBER ()
                      OVER (PARTITION BY deptNo ORDER BY deptNo, eName)
              FROM scott.emp) d
START WITH d.rnum = 1
CONNECT BY d.rnum = PRIOR d.rnum + 1 AND PRIOR d.deptNo = d.deptNo
  GROUP BY d.deptNo

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