How do I handle this tricky MySQL query [Concatenate based on priority from same table]?

Question

Before diving into a Python script to do this for me, I am wondering if we can achieve this via a MySQL query alone?

I have a table with multiple records per ID. I want to concatenate the multiple values into one record and concatenate based on priority? Still with me?

A table might help :

ID Value Priority
1  AA    1
1  KK    3
1  CC    2 
2  AA    1
3  EE    4  
3  FF    5 
2  HH    6

Desired Output :

ID Concat_Value 
1  AA, CC, KK
2  AA, HH
3  EE, FF

Priority goes in an increasing order. Smaller the number, higher the priority.

Answer 1

Easy as pie.

SELECT id, GROUP_CONCAT(`value` ORDER BY priority) as concat_value
FROM table1
GROUP BY id

See: http://dev.mysql.com/doc/refman/5.0/en/group-by-functions.html#function_group-concat

If you want a space in the group_concat, you'll have to change the separator:

SELECT 
  id
  , GROUP_CONCAT(`value` ORDER BY priority SEPARATOR ', ') as concat_value
FROM table1
GROUP BY id