 <p>First line -- a table scan (see NULLs and ALL)</p> <p>2nd and 4th line -- an index scan ("Using index"), but rather costly since 10K rows needed.</p> <p>What it does not tell you is whether some other index(es) would be more efficient. Nor does it tell you whether reformulating the query would help. Please provide us with the SELECT so we can help you there, plus tie more things to the EXPLAIN.</p> <p>More links:<br> <a href="http://myxplain.net/" rel="nofollow">http://myxplain.net/</a><br> <a href="http://www.sitepoint.com/using-explain-to-write-better-mysql-queries/" rel="nofollow">http://www.sitepoint.com/using-explain-to-write-better-mysql-queries/</a></p>