How to Exclude NULL Values from GROUP BY Queries While Preserving All Rows?

GROUP BY Query Excluding NULL Values

When utilizing the GROUP BY function to aggregate data, you may encounter a scenario where you need to exclude NULL values from the grouping operation. This typically occurs when you want to preserve all rows with NULL values in the specified field.

To achieve this, one approach is to replace NULL values with a unique identifier. This can be done using the IFNULL() function:

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

In this example, we replace NULL ancestors with a unique UUID() value. This ensures that NULL ancestors won't be grouped together, and the query will return all rows regardless of their ancestor field value.

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