MySQL GROUP_CONCAT with Nulls

group-concat, mysql

Solution

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.

Problem

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).

Original source