MYSQL / PHP query to return alphabetical listing

trying to return a recordset where the first letter of a field value is a predetermined letter of the alphabet:

$data = mysql_query("SELECT * FROM physicians WHERE Left(lastName, 1) = '$sv' 

This almost seems to work but is buggy. I have database records where ‘lastName’ starts with an ‘s’, but will not show up if I throw ‘s’ or ‘S’ at this query as the value of the $sv variable.

If I re-enter that record in the database, i may or may not get that record to show up when i pass “s”.

The records are in there because if I run a different query on a different field, they show up…

I’m sure there’s more to returning query results alphabetically that i’m missing… can anyone help?

My field type is varchar if that helps…