How many different production codes does the episode originally aired on October 18, 1984 have?
CREATE TABLE table_2818164_2 (production_code VARCHAR, original_air_date VARCHAR)
SELECT COUNT(production_code) FROM table_2818164_2 WHERE original_air_date = "October 18, 1984"
<s>[INST] Write mssql query to answer the following question given the database schema. Schema: CREATE TABLE table_2818164_2 (production_code VARCHAR, original_air_date VARCHAR) Question: How many different production codes does the episode originally aired on October 18, 1984 have? [/INST] SELECT COUNT(production_code) FROM table_2818164_2 WHERE original_air_date = "October 18, 1984" </s>