Optimizing a SELECT statement with ORDER BY by using indices
<p>I have these queries:</p>

<p>1st query:</p>

<pre><code>SELECT (..) FROM db WHERE A = const AND B &gt; const AND C &gt;= const ORDER BY B DESC LIMIT const
</code></pre>

<p>2nd query (different db):</p>

<pre><code>SELECT (...) FROM db' WHERE A' = const ORDER BY X' DESC LIMIT const
</code></pre>

<p>Question about 1st query:
Is it sufficient to have a multiple row index (A, B, C) or do I need an additional single row index (B) (or a different one) because of the <code>ORDER BY</code>statement?</p>

<p>Question about 2nd query: Do I need a multiple row index (A', X') or two single row indices (A'), (X') to make us of them in this query?</p>