asp.net - How to replace diacrita charaters from other master table in sql server -

i wanna implement export flat file functionality through asp.net following conditions:

check every column each rows of table diacritic character   if exists  value diacritic char master table          if exists                replace          else               add diacritic character master table null value                , remove record resultset 

i wanna implement functionality in t-sql.so please guide me on issue considering performance too.