GROUP BY – do not group NULL

by

Perhaps you should add something to the null columns to make them unique and group on that? I was looking for some sort of sequence to use instead of UUID() but this might work just as well.

SELECT `table1`.*, 
    IFNULL(ancestor,UUID()) as unq_ancestor
    GROUP_CONCAT(id SEPARATOR ',') AS `children_ids`
FROM `table1` 
WHERE (enabled = 1) 
GROUP BY unq_ancestor

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