SCHEMA:
CREATE TABLE table_name_6 (yr_plyf INTEGER, g_plyf VARCHAR, coach VARCHAR)
USER:
What is the sum of the yr plyf of coach ed robinson, who has a G plyf of 0?

QUERY:
SELECT SUM(yr_plyf) FROM table_name_6 WHERE g_plyf = 0 AND coach = "ed robinson"