-- Change DBTableName to database table name 
-- Change DBTextField to database table field name 
-- Change 'SearchText' to text desired to be changed 
-- like 'DefaultCode001'
-- Change 'ReplaceText' to actual text to be replaced 
-- like 'ActualCode001'

UPDATE DBTableName
SET DBTextField = REPLACE(CAST(DBTextField AS varchar(MAX)), 'SearchText', 'ReplaceText')
FROM TableName
WHERE CHARINDEX('SearchText',CAST(DBTextField as varchar(MAX)))>0