Why did MatchUp not catch some duplicates?
MatchUp can only use the match rules and settings which the end user has provided, so verify the matchkeys got built correctly. If this wasnt the source of your problem, check to see if your matchcode rules were satisfied the keys may be the same, but you may not have met the conditions of any matchcode column. Because the Object also allows for real time comparison, inferred matching can not always be taken advantage of. In other words, the sequence of a linking record is more critical with the API. 2.7.5 I got way too many duplicates! Most likely, your matchcode rules were too loose; possibly one column of your matchcode was a subset of a valid column. Another source of too many duplicates may be that you mapped in the wrong datatype in the AddMapping method, or supplied the incorrect source data in the Addfield method. If you are using a Last Name as part of your match, but you accidentally mapped in a Full Name field and datatype, you will get too many duplicates.
