How to identify duplicate attribute value in Transaction matching

Summary:

For bank data, the requirement is to load duplicate check numbers but also we need to identify transactions which have duplicate check numbers and populate an attribute as 'Duplicate'.

Content (required):

For bank data, the requirement is to load duplicate check numbers but also we need to identify transactions which have duplicate check numbers and populate an attribute as 'Duplicate'. The "Key" feature won't be useful here, as it would restrict loading transactions with duplicate check numbers.

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