dla: I *SHOWED* you the error. Look at the word voltage in red in my last post. SQL Server does NOT KNOW which "voltage" you mean by that one. Put the table alias in front of it.
But ALSO read what I wrote about LEFT JOIN being converted to INNER JOIN by your other mistake.
An optimist sees the glass as half full.
A pessimist sees the glass as half empty.
A realist drinks it no matter how much there is.