instruction: tell me the average systemicsystolic of patient 005-87465 on this month/20?
response: SELECT AVG(vitalperiodic.systemicsystolic) FROM vitalperiodic WHERE vitalperiodic.patientunitstayid IN (SELECT patient.patientunitstayid FROM patient WHERE patient.patienthealthsystemstayid IN (SELECT patient.patienthealthsystemstayid FROM patient WHERE patient.uniquepid = '005-87465')) AND NOT vitalperiodic.systemicsystolic IS NULL AND DATETIME(vitalperiodic.observationtime, 'start of month') = DATETIME(CURRENT_TIME(), 'start of month', '-0 month') AND STRFTIME('%d', vitalperiodic.observationtime) = '20'