SQL Server forces determinism here: anything projected when there is a GROUP BY must be one of the grouping properties, an aggregate, or a constant. mySql does

SQL Server forces determinism here: anything projected when there is a GROUP BY must be one of the grouping properties, an aggregate, or a constant. mySql does allow other columns to be projected, which has always felt wrong to me as I like my results from the DB to be dertemanistic. I wasn't aware sqlite allowed it too, though I've not directly used sqlite much. It is something that causes issues migrating to other DBs (or when trying to be cross-DB compatible). Often it is used accidentally and by chance gives good results, where is is used deliberately IME it is where the same value will always return due to properties of the that data being queried (in which case the "fix" for other DBs is to use an aggregate like MIN or MAX). Sometimes accidentally use leads to subtle bugs which, as you say, can be rather dangerous. Note though that these days this can only be used dangerously if the ONLY_FULL_GROUP_BY option is on, and it is off by default. Allowing it in safe circumstances actual makes modern mySql more standards compliant in this respect, see https://dev.mysql.com/doc/refman/8.0/en/group-by-handling.html https://dev.mysql.com/doc/refman/8.0/en/group-by-handling.ht... for more detail.