https://www.db-fiddle.com/f/igDh3aJEXRLZEkL7eNrcnc/0
CREATE FUNCTION get_tinyint(MY_BOOLEAN tinyint) RETURNS TINYINT(1)
RETURN COALESCE(MY_BOOLEAN, 0);
CREATE OR REPLACE VIEW TEST_VIEW AS
SELECT
T1.ID AS ID,
get_tinyint(T2.MY_BOOLEAN) AS MY_BOOLEAN
FROM
TEST1 T1 LEFT JOIN TEST2 T2 ON T1.ID=T2.TEST1_ID;