There are many errors in The Raiser's Edge that can be be corrected by running the Fix Constituent Code Plugin, as constituency codes are widely used in The Raiser's Edge.
How does the Fix Constituent Code Sequence Utility work?
It goes into the table that holds the constituent codes, affectionately called CONSTITUENT_CODES, and then it pulls the constituent_id from that table and starts at 1 and renumbers them all the way down until it's finished. So constituent 1 will have their constituent codes re-ordered from 1 to N, where N is the number of constituent codes associated with them. Then we will reset the sequence counter to 1 and move onto to constituent 2 and repeat the process.