Obtain Person (or system default) UID_DialogCulture

Environment: 1IM 9.2

We need to provide an external REST API consumer with Person data including Culture information for every active Person in our database.

For this we created a a ReadOnly View that contains Person and QBMCulture info among others (exposed through api/entities endpoint in App ServerREST API),

In the process we found UID_DialogCulture is only written in Person records when a language is manually selected, how can i get default system Culture for the rest of the records ? Using SQL if posible.. 

Thks in advance

Hector