Table schema:
CREATE TABLE table_name_17 (destroyed INTEGER, survived VARCHAR, to_iran VARCHAR, damaged VARCHAR)

Question: What's the average destroyed with a 1990 over 12, more than 1 damaged, 6 survivors, and a to Iran less than 4?
SQL: SELECT AVG(destroyed) FROM table_name_17 WHERE 1990 > 12 AND damaged > 1 AND to_iran < 4 AND survived = 6