Referer_type in matomo_log_visit has boolean value instead of INT values

I installed Matomo on premise and want to write a SQL query to select the channels/referrer.

According to the API Reference the referrer is stored in the log_visit table under referer_type and it should contain INT value. in my log_visit table referer_type is a boolean field. the referrer is not anonymized in Matomo.
In the Matomo dashboard the channel type are correctly shown.

Is it correct that the field is of type boolean? How can i query the channels?