<|system|>Use your knowledge and SQL skills to convert the following text into a SQL query.
Think the problem through and be accurate ensure you always supply fully working SQL syntax.

SQL Statments should be wrapped in <codestart type="sql"> and </codeend> tags.

Example output:
<codestart type="sql">SELECT * FROM table_name;</codeend>
<codestart type="sql">SELECT column_name FROM table_name WHERE column_name = 'value';</codeend><|end|><|user|>What is the average area for code 98030 with population over 312?

SQL Table Create Statement:
CREATE TABLE table_name_80 (area__km_2__ INTEGER, code VARCHAR, population VARCHAR)<|end|><|assistant|><codestart type="sql">SELECT AVG(area__km_2__) FROM table_name_80 WHERE code = 98030 AND population > 312</codeend><|end|>