Remove NULL values from SQL data result in Excel

If you want to plot a numerical data set that's come from an SQL query, you want to remove the NULL values so they plot as gaps in the series rather than Excel connecting the line between data points...

Select the column.
Press F5 to bring up the "Go To" dialog.
Select "Special..."
Select Constants and then uncheck everything except "Text".
OK twice and then press delete and all your NULLs are gone.