What is the key column for joining FND_BPM_TASK_B and PO_HEADERS_ARCHIVE_ALL?

Summary:

What is the key column for joining FND_BPM_TASK_B and PO_HEADERS_ARCHIVE_ALL?

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Hi Experts,

I found the piece of info from CCC that the PR's Comment History can be retrieved from tables of:
FUSION.FND_BPM_TASK_B T, FUSION.POR_REQUISITION_HEADERS_ALL PRH, FUSION.FND_BPM_TASK_COMMENT TA
The full SQL is:

SELECT DISTINCT PRH.REQUISITION_NUMBER, PRH.DESCRIPTION,PRH.DOCUMENT_STATUS,
TA.COMMENT_BY, TA.COMMENT_TEXT, TA.COMMENT_DATE,
T.STATUS_CODE,T.OUTCOME_CODE, T.INITIATED_BY, T.INITIATED_DATE, T.COMPLETED_BY, T.TASK_NUMBER