CREATE TABLE table_28164986_4 (date_of_vacancy VARCHAR2, outgoing_manager VARCHAR2)

how many times did tunde abdulrahman leave the team?
SELECT COUNT(date_of_vacancy) FROM table_28164986_4 WHERE outgoing_manager = "Tunde Abdulrahman"
SELECT COUNT("date_of_vacancy") FROM "table_28164986_4" WHERE "Tunde Abdulrahman" = "outgoing_manager"