I can’t compare an arithmetic mean, so I can use select

Question

I’m using postgresql to do the select of an attribute called val_unit of a name table produto.

I use having avg(val_unit) > val_unit or where avg(val_unit) to select only the val_unit that stays within the average of everyone, but just doesn’t give.

Mine selects:

select descricao_produto from produto where val_unit < avg(val_unit);

select descricao_produto form produto having val_unit < avg(val_unit);