andWhere surrounding quotes

I am using an andWhere in a find (use to populate a dropDownList.

->andWhere(['lst_pilot_car_items.CurrencyCode' =>; 'clients.CurrencyCode'])

but it results in

AND (lst_pilot_car_items.CurrencyCode='clients.CurrencyCode')

which does work. If I remove the single quotes, then the query works

AND (lst_pilot_car_items.CurrencyCode=clients.CurrencyCode)

So my question is: why are these single quotes being generated and how can I solve this?

Thank you.

Nevermind, I finally figured it out. For anyone else facing this issue, the solution was