How many stroke patients have married?
stroke refers to conditions where DESCRIPTION = 'Stroke'; married refers to the marital status of the patient in which marital = 'M';
SELECT COUNT(DISTINCT T1.patient) FROM patients AS T1 INNER JOIN conditions AS T2 ON T1.patient = T2.PATIENT WHERE T2.DESCRIPTION = 'Stroke' AND T1.marital = 'M'