mirabilos <tg@xxxxxxxxxxx> writes: > This works well. However, what I seem to be not allowed to do is > (without the extra COALESCE, to simplify): > ... > This is because, when I use DISTINCT (but only then‽), the ORDER BY > arguments must be… arguments to the function, or something. Well, yeah. Simplify it to SELECT array_agg(DISTINCT x ORDER BY y) FROM mytable; If there are several rows containing the same value of x and different values of y, which y value are we supposed to sort the unique-ified x value by? It's an ill-defined query. For the specific example you give, it's true that any specific possible output of jsonb_build_object() would correspond to a unique set of cot.weekday, cot.from_hour, cot.to_hour values. But the parser can't be expected to know that. Many functions can produce the same output for different sets of inputs. I'd suggest moving the distinct-ification into an earlier processing step (i.e. a sub-select), or maybe thinking harder about why you're getting duplicates in the first place. regards, tom lane
