Context: CREATE TABLE table_name_19 (area__km²_ INTEGER, density___km²_ VARCHAR, official_website VARCHAR)
Question: What is the sum of the area values for districts having density over 462 and websites of http://krishna.nic.in/?
Answer: SELECT SUM(area__km²_) FROM table_name_19 WHERE density___km²_ > 462 AND official_website = "http://krishna.nic.in/"