Re: Strange behavior with a strange request

[Rick James]

GROUP BY id AND id > 3
means
GROUP BY ((id) AND (id > 3))
Assuming that id is INT and NOT NULL, then
AND is expecting boolean value on either side,
(id), when treated as a boolean, is TRUE if id != 0, else FALSE; so, probably it is always TRUE.
(id > 3) will be FALSE for some small values, else TRUE.

So, it is GROUPing BY FALSE when id = 1,2,3; and GROUPing BY TRUE for bigger values. That is, there are only two groups.

If it is deliberate, it is too painfully clever, and obfuscative.

I would call it a coding mistake, not a bug in MySQL.