if you want to retrieve unique records you have to enable the Distinct Property on the desired View Component (e.g. List) or on the Selector.
Objects with duplicate attribute values are removed from the content of the list. The columns included in the distinct clause are: all component Display Attributes, Sort Attributes and all columns used as output parameters.
For example if in your page you have a Form with a Selection Field related to products and you want to populate it with unique data retrieved by a Selector, you have to enable the Distinct Property (in the General tab of the Properties View) on the Selector.
In this way the items (products) shown in the dropdown menu field (Selection Field) will be unique.