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 (area__km_2__ INTEGER, code VARCHAR, population VARCHAR)

### Question ###
What is the average area for code 98030 with population over 312?

### Accurate SQL ###

SELECT AVG(area__km_2__) FROM table_name_80 WHERE code = 98030 AND population > 312