SQL Query to concatenate column values from multiple rows in Oracle

Question

Would it be possible to construct SQL to concatenate column values from multiple rows?

The following is an example:

Table A

PID
A
B
C

Answer 1

There are a few ways depending on what version you have - see the oracle documentation on string aggregation techniques. A very common one is to use LISTAGG:

SELECT pid, LISTAGG(Desc, ' ') WITHIN GROUP (ORDER BY seq) AS description
FROM B GROUP BY pid;

Then join to A to pick out the pids you want.

Note: Out of the box, LISTAGG only works correctly with VARCHAR2 columns.