instruction: what is the number of patients whose days of hospital stay is greater than 6 and lab test name is asparate aminotransferase (ast)?
response: SELECT COUNT(DISTINCT demographic.subject_id) FROM demographic INNER JOIN lab ON demographic.hadm_id = lab.hadm_id WHERE demographic.days_stay > "6" AND lab.label = "Asparate Aminotransferase (AST)"