Merge pull request #4159 from soerenwolfers/patch-36

Update order_preservation.md

Author: szarnyasg

docs/sql/dialect/order_preservation.md

@@ -57,8 +57,8 @@ The following operations **do not** guarantee that the row order is preserved:
 * `JOIN`
 * `SAMPLE`
 * `UNION`
-* `GROUP BY`
-* `ORDER BY`
+* `GROUP BY` (in particular, the output order is undefined and the order in which rows are fed into [order-sensitive aggregate functions](https://duckdb.org/docs/sql/functions/aggregates.html#order-by-clause-in-aggregate-functions) is undefined unless explicitly specified in the aggregate function)
+* `ORDER BY` (specifically, `ORDER BY` may not use a [stable algorithm](https://en.m.wikipedia.org/wiki/Stable_algorithm))
 
 ## Insertion Order