```json { "classifications": [ {"column": "STUDYID", "label": "none", "confidence": 1.0, "reason": "Single constant value, not a key"}, {"column": "USUBJID", "label": "primary_key", "confidence": 1.0, "reason": "100% distinct (306/306), zero nulls, unique subject identifier"}, {"column": "SUBJID", "label": "near_key", "confidence": 0.95, "reason": "100% distinct (306/306), zero nulls, but likely part of composite key with STUDYID"}, {"column": "RFSTDTC", "label": "none", "confidence": 1.0, "reason": "Date field with 206 distinct values, not a key"}, {"column": "RFENDTC", "label": "none", "confidence": 1.0, "reason": "Date field with 212 distinct values, not a key"}, {"column": "RFXSTDTC", "label": "none", "confidence": 1.0, "reason": "Date field with 206 distinct values, not a key"}, {"column": "RFXENDTC", "label": "none", "confidence": 1.0, "reason": "Date field with 212 distinct values, not a key"}, {"column": "RFICDTC", "label": "none", "confidence": 1.0, "reason": "Single constant value, not a key"}, {"column": "RFPENDTC", "label": "none", "confidence": 1.0, "reason": "Date field with 296 distinct values, not a key"}, {"column": "DTHDTC", "label": "none", "confidence": 1.0, "reason": "Death date with only 4 distinct values, not a key"}, {"column": "DTHFL", "label": "none", "confidence": 1.0, "reason": "Binary flag with 2 values, not a key"}, {"column": "SITEID", "label": "foreign_key", "confidence": 0.9, "reason": "17 distinct values, likely references site dimension table"}, {"column": "AGE", "label": "none", "confidence": 1.0, "reason": "Demographic attribute with 37 distinct values"}, {"column": "AGEU", "label": "none", "confidence": 1.0, "reason": "Single constant value (YEARS), not a key"}, {"column": "SEX", "label": "none", "confidence": 1.0, "reason": "Binary demographic attribute, not a key"}, {"column": "RACE", "label": "none", "confidence": 1.0, "reason": "Categorical attribute with 4 values, not a key"}, {"column": "ETHNIC", "label": "none", "confidence": 1.0, "reason": "Binary demographic attribute, not a key"}, {"column": "ARMCD", "label": "none", "confidence": 1.0, "reason": "Treatment arm code with 4 values, not a key"}, {"column": "ARM", "label": "none", "confidence": 1.0, "reason": "Treatment arm description with 4 values, not a key"}, {"column": "ACTARMCD", "label": "none", "confidence": 1.0, "reason": "Actual treatment arm code with 4 values, not a key"}, {"column": "ACTARM", "label": "none", "confidence": 1.0, "reason": "Actual treatment arm description with 4 values, not a key"}, {"column": "COUNTRY", "label": "none", "confidence": 1.0, "reason": "Single constant value (USA), not a key"}, {"column": "DMDTC", "label": "none", "confidence": 1.0, "reason": "Date field with 237 distinct values, not a key"}, {"column": "DMDY", "label": "none", "confidence": 1.0, "reason": "Study day with 27 distinct values, not a key"}, {"column": "TRT01P", "label": "none", "confidence": 1.0, "reason": "Planned treatment with 4 values, not a key"}, {"column": "TRT01A", "label": "none", "confidence": 1.0, "reason": "Actual treatment with 4 values, not a key"}, {"column": "TRTSDTM", "label": "none", "confidence": 1.0, "reason": "Treatment start datetime with 206 distinct values, not a key"}, {"column": "TRTSTMF", "label": "none", "confidence": 1.0, "reason": "Time imputation flag with 2 values, not a key"}, {"column": "TRTEDTM", "label": "none", "confidence": 1.0, "reason": "Treatment end datetime with 212 distinct values, not a key"}, {"column": "TRTETMF", "label": "none", "confidence": 1.0, "reason": "Time imputation flag with 2 values, not a key"}, {"column": "TRTSDT", "label": "none", "confidence": 1.0, "reason": "Treatment start date with 206 distinct values, not a key"}, {"column": "TRTEDT", "label": "none", "confidence": 1.0, "reason": "Treatment end date with 212 distinct values, not a key"}, {"column": "TRTDURD", "label": "none", "confidence": 1.0, "reason": "Treatment duration with 117 distinct values, not a key"}, {"column": "SCRFDT", "label": "none", "confidence": 1.0, "reason": "Screen failure date with 49 distinct values, not a key"}, {"column": "EOSDT", "label": "none", "confidence": 1.0, "reason": "End of study date with 212 distinct values, not a key"}, {"column": "EOSSTT", "label": "none", "confidence": 1.0, "reason": "End of study status with 3 values, not a key"}, {"column": "FRVDT", "label": "none", "confidence": 1.0, "reason": "Follow-up visit date with 36 distinct values, not a key"}, {"column": "RANDDT", "label": "none", "confidence": 1.0, "reason": "Randomization date with 206 distinct values, not a key"}, {"column": "DTHDT", "label": "none", "confidence": 1.0, "reason": "Death date with 4 distinct values, not a key"}, {"column": "DTHDTF", "label": "none", "confidence": 1.0, "reason": "Single constant value, not a key"}, {"column": "DTHADY", "label": "none", "confidence": 1.0, "reason": "Death analysis day with 4 distinct values, not a key"}, {"column": "LDDTHELD", "label": "none", "confidence": 1.0, "reason": "Last dose to death elapsed days with 4 values, not a key"}, {"column": "DTHCAUS", "label": "none", "confidence": 1.0, "reason": "Death cause with 4 distinct values, not a key"}, {"column": "DTHDOM", "label": "none", "confidence": 1.0, "reason": "Death domain with 2 values, not a key"}, {"column": "DTHCGR1", "label": "none", "confidence": 1.0, "reason": "Death category with 2 values, not a key"}, {"column": "LSTALVDT", "label": "none", "confidence": 1.0, "reason": "Last alive date with 211 distinct values, not a key"}, {"column": "SAFFL", "label": "none", "confidence": 1.0, "reason": "Safety flag with 2 values, not a key"}, {"column": "RACEGR1", "label": "none", "confidence": 1.0, "reason": "Race group with 2 values, not a key"}, {"column": "AGEGR1", "label": "none", "confidence": 1.0, "reason": "Age group with 2 values, not a key"}, {"column": "REGION1", "label": "none", "confidence": 1.0, "reason": "Single constant value (NA), not a key"}, {"column": "LDDTHGR1", "label": "none", "confidence": 1.0, "reason": "Last dose to death group with 2 values, not a key"}, {"column": "DTH30FL", "label": "none", "confidence": 1.0, "reason": "Death within 30 days flag with 2 values, not a key"}, {"column": "DTHA30FL", "label": "none", "confidence": 1.0, "reason": "Single constant value, not a key"}, {"column": "DTHB30FL", "label": "none", "confidence": 1.0, "reason": "Death before 30 days flag with 2 values, not a key"} ] } ```