instruction: how many patients until 4 years ago were diagnosed with failure to wean in the same hospital visit after a procedure of anticonvulsant - valproate?
response: SELECT COUNT(DISTINCT t1.uniquepid) FROM (SELECT patient.uniquepid, treatment.treatmenttime, patient.patienthealthsystemstayid FROM treatment JOIN patient ON treatment.patientunitstayid = patient.patientunitstayid WHERE treatment.treatmentname = 'anticonvulsant - valproate' AND DATETIME(treatment.treatmenttime) <= DATETIME(CURRENT_TIME(), '-4 year')) AS t1 JOIN (SELECT patient.uniquepid, diagnosis.diagnosistime, patient.patienthealthsystemstayid FROM diagnosis JOIN patient ON diagnosis.patientunitstayid = patient.patientunitstayid WHERE diagnosis.diagnosisname = 'failure to wean' AND DATETIME(diagnosis.diagnosistime) <= DATETIME(CURRENT_TIME(), '-4 year')) AS t2 WHERE t1.treatmenttime < t2.diagnosistime AND t1.patienthealthsystemstayid = t2.patienthealthsystemstayid