How To: Trim leading and trailing spaces from string field values
Extra spaces at the beginning or end of string field values prevent operations such as joining, linking, and geocoding on tables from working correctly. You can remove these spaces by applying the Trim request in the field calculator.
Open the table and click Start Editing if necessary.
Select the string field you want to trim.
Click the Field Calculator button.
Double-click the field name to be trimmed from the Fields list.
Set the Type to String.
Scroll down the Requests list and double click Trim. The final expression should look similar to this:
Click Table > Stop Editing and choose to save the edits.