Who wrote the episode that had 12.15 million viewers?
CREATE TABLE table_24961421_1 (written_by VARCHAR, us_viewers__millions_ VARCHAR)
SELECT written_by FROM table_24961421_1 WHERE us_viewers__millions_ = "12.15"
<s>[INST] Write mssql query to answer the following question given the database schema. Schema: CREATE TABLE table_24961421_1 (written_by VARCHAR, us_viewers__millions_ VARCHAR) Question: Who wrote the episode that had 12.15 million viewers? [/INST] SELECT written_by FROM table_24961421_1 WHERE us_viewers__millions_ = "12.15" </s>