When attempting to merge duplicate Constituent Records, the following Merge Error is received:
Data could not be saved. The UPDATE statement conflicted with the CHECK constraint 'CK_REGISTRANT_VALIDATTENDED'. The conflict occurred in database 'database name', table 'dbo.REGISTRANT'.
Definition for the check constraint: ([WILLNOTATTEND]=(0) OR [ATTENDED]=(0))
With the above definition, this tells us that both of these constituents are registered for the same event. I recommend checking the event/s they are each registered for, removing the constituent that you no longer need in the system (that will be merged into the other record) from being registered from the event, then attempt the merge process again.
This should resolve for the check constraint and allow for the duplicate merge to complete successfully.
Steps to Duplicate
Go to Constituents > Duplicates
Click Merge two Constituents
Enter the Source and Target Constituent record
Select your Merge Configuration
Choose the appropriate option, as per your Business needs, for "Delete source constituent" or "Mark source constituent inactive"