Is there an option to make MySQL's Group_Concat function include nulls?
Consider the following example from my source table:
userId, questionId, selectionId
7, 3, NULL
7, 4, 1
7, 5, 2
When I query on the selection table with GROUP_CONCAT, I get the following:
7, 4=1,5=2
I would like to get the following:
7, 3=NULL,4=1,5=2
For reference, my query looks like this:
Select userId, GROUP_CONCAT(CONCAT(questionId, '=', selectionId))
From selection
Group by userId;
I also tried adding an IFNULL like this:
Select userId, GROUP_CONCAT(IFNULL(CONCAT(questionId, '=', selectionId), 'NULL'))
From selection
Group by userId;
but that produced the following:
7, NULL,4=1,5=2
Note - There is one other complexity that I forgot to include. The selectionId is a foreign key to another table. I use a left outer join to the selection_text table. My real query includes fields from that table (these fields resolve to NULL since the selectionId is null).
Answer
You should just IFNULL the column that can be NULL;
SELECT userId, GROUP_CONCAT(CONCAT(questionId, '=',
IFNULL(selectionId, 'NULL')))
FROM selection
GROUP BY userId;
Demo here.