Be careful when you update records by way of an import. There is no undo so make sure you have a good backup. Here's how the two features work:
Update Existing Records in Found Set
Let's say you have ten records in your database. You just performed a search so now there are six records in your current found set. You have an import file that also contains six records. Under this option, the values in the imported records will replace the values in the existing records in position order. IOW, the first record in your import file will update the first record in your found set; the second record in your import file will update the second record in your found set; etc, etc, until you reach the end.
If you have more records in your import file than you do in your found set, use the checkbox "add remaining data as new records" to instruct the database whether to add or disregard them.
I would not recommend using this option unless you can be absolutely sure the order of the records in both found set and import file are identical. This is difficult to guarantee, what if your import file is sorted in a way you can't recall or recreate in your database?
Update Matching Records in Found SetThis is the preferred method of updating records with an import. For this to work, your import file has a field with a unique identifier that corresponds to a field in your database with the same unique identifier. When you select this option you must map the ID fields then click again until the arrow is bi-directional. Under this method, the order of your records is irrelevant. The imported data will hunt down and update its matching record.
If you have records in your import file that do not have a match in your found set, use the checkbox "add remaining data as new records" to instruct the database whether to add or disregard them.
Under Both Features
- Only the records in your found set will be effected by the import.
- Only the fields you map will be effected by the import.
- If a field in your found set contains a value while the imported field is empty, the resulting field will be empty.