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When you change the structure of a table, the Table designer uses the field name and field position to determine how to transfer information to the new structure.

Warning!

If it cannot find a corresponding field in the new table, the Table designer does not copy the data from the fields in the backup table; instead, the information is lost when the backup table is deleted.

To prevent losing data that you want to keep, save the table structure frequently as you make changes and confirm that they are completed successfully.

If you change the type of a field, the Table designer does its best to convert data to the new type. Some conversions are relatively straightforward, such as converting date, logical or numeric fields to character. However, radical conversions (such as a memo field to a date field) might produce results you don’t want. In addition, the Table designer does not copy data that is invalid in the new field type. For example, attempting to copy the value "123ABC" from a character field to a numeric field fails because letters aren’t valid entries in numeric fields.

In addition to these guidelines, remember that if you delete a field in a table that contains rows, you lose the information in that field permanently. You can recover the information only if you have made a backup of the table.