Below is the list of tables from the database along with their columns and datatype. Need to generate an accurate SQL query for the question.
Only use the columns present in the respective table. Only use the columns which are required to generate the SQL query. Only use table joins if required and not otherwise.

### Tables ###
TABLE: CREATE TABLE table_name_80 (year INTEGER, date VARCHAR, designated_home VARCHAR)

### Question ###
What year had a date of TBA where the Oakland raiders were the home team?

### Accurate SQL ###

SELECT AVG(year) FROM table_name_80 WHERE date = "tba" AND designated_home = "oakland raiders"