Who wrote the episode with the production code 519?
CREATE TABLE table_21550897_1 (written_by VARCHAR, production_code VARCHAR)
SELECT written_by FROM table_21550897_1 WHERE production_code = 519
<s>[INST] Write mssql query to answer the following question given the database schema. Schema: CREATE TABLE table_21550897_1 (written_by VARCHAR, production_code VARCHAR) Question: Who wrote the episode with the production code 519? [/INST] SELECT written_by FROM table_21550897_1 WHERE production_code = 519 </s>