@Alex Pairol Check out this example page that I created a little while back.
What it does is creates a drop down list based upon a specific column in a dataset used by the rest of the page.
The example provides a class called dropDownData that is used to manipulate the dataset and return a dropdown value list based upon a specific column (property key) in a dataset. The constructor takes the dataset returned from wix-dataset.getItems() call. The getItems call asks for all items in the dataset by setting the range for getItems to 0 - wix-dataset.getTotalCount().
When a specific column for a drop down is needed the object created from the class uses named helper functions (e.g.servicesList()) which call the column filter function uniqueColumnListForField(field) with the name of the column to be used for the drop down.
This function returns an array of option objects that can be assigned directly to the dropdown options property.
Hope this answers your question.
Steve