instruction: give me the number of patients on po/ng route of drug administration who have insomnia nos diagnoses.
response: SELECT COUNT(DISTINCT demographic.subject_id) FROM demographic INNER JOIN diagnoses ON demographic.hadm_id = diagnoses.hadm_id INNER JOIN prescriptions ON demographic.hadm_id = prescriptions.hadm_id WHERE diagnoses.short_title = "Insomnia NOS" AND prescriptions.route = "PO/NG"