Apart from what others have said, in case when you are required to delete one record from the database you have to pass something to check against;
a primary key is prefered. The code that you are using must be changed to:
DELETE FROM Total WHERE [Report] IS NULL
Dave gave you an idea of this, SQL expects you to tell what records to delete. Otherwise, it will simply delete the entire list of records. If, somehow you wanted to delete the column, you can instead alter the table and remove the column (if that is what is intended). That command would be like this,
ALTER TABLE Total DROP COLUMN [Report]
This will remove that column.
Edit
Since you wanted to remove the data in that column, instead of doing anything I would recommend
UPDATE
-ing the fields. You can do so in SQL, like this,
UPDATE Total SET [Report] = NULL
This will update the (entire —
is this what you want?) table and set it to NULL. If you want to set a record or two to NULL, then try passing a WHERE clause there.