How to: Exclude Duplicate Rows (Visual Database Tools)
If you want to see only unique values in a result set, you can specify that you want to exclude duplicates from the result set.
To exclude duplicate rows from the result set
Right-click the background of the Diagram pane, then choose Properties from the shortcut menu.
In the Property window, click Distinct values and set the value to Yes.
The Query and View Designer inserts the keyword DISTINCT in front of the list of display columns in the SQL statement.
Note
If you use the DISTINCT keyword you may not be able to modify the result set in the results pane.