Among all the patients who once had cystitis, what was the percentage of them being married?
DIVIDE(COUNT(marital = 'M'), COUNT(patient)) as percentage where DESCRIPTION = 'Cystitis';

SELECT CAST(SUM(CASE WHEN T1.marital = 'M' THEN 1 ELSE 0 END) AS REAL) * 100 / COUNT(DISTINCT T1.patient) FROM patients AS T1 INNER JOIN conditions AS T2 ON T1.patient = T2.PATIENT WHERE T2.description = 'Cystitis'