CREATE TABLE table_name_80 (year NUMBER, date VARCHAR2, designated_home VARCHAR2)

What year had a date of TBA where the Oakland raiders were the home team?
SELECT AVG(year) FROM table_name_80 WHERE date = "tba" AND designated_home = "oakland raiders"
SELECT AVG("year") FROM "table_name_80" WHERE "date" = "tba" AND "designated_home" = "oakland raiders"