Database
[{"MGESAD":"6095 - NCAM - US - GIUTCB - US Consumer Bank - USRB"}]
Query
db.collection.update({},[{"$set":{"MGESAD":{"$substrCP":["$MGESAD",0,{"$indexOfCP":["$MGESAD"," - "]}]},"MGE_DESC":{"$substrCP":["$MGESAD",{"$add":[{"$indexOfCP":["$MGESAD"," - "]},3]},{"$strLenCP":"$MGESAD"}]}}}],{"multi":true})