How many different original air dates did the episode number 6 have? 
CREATE TABLE table_13426649_1 (original_air_date VARCHAR, _number VARCHAR)
SELECT COUNT(original_air_date) FROM table_13426649_1 WHERE _number = 6
<s>[INST] Write mssql query to answer the following question given the database schema. Schema: CREATE TABLE table_13426649_1 (original_air_date VARCHAR, _number VARCHAR) Question: How many different original air dates did the episode number 6 have?  [/INST] SELECT COUNT(original_air_date) FROM table_13426649_1 WHERE _number = 6 </s>