"key_len" column is more important or "rows" column in the result of EXPLAIN?
<p>I have executed a query with two different kind of indexes. Here is the result of them:</p>

<p><strong>First kind of index:</strong></p>

<p><a href="https://i.stack.imgur.com/1Iqtj.png" rel="nofollow noreferrer"><img src="https://i.stack.imgur.com/1Iqtj.png" alt="enter image description here"></a></p>

<p><strong>Second kind of index:</strong></p>

<p><a href="https://i.stack.imgur.com/PEzMf.png" rel="nofollow noreferrer"><img src="https://i.stack.imgur.com/PEzMf.png" alt="enter image description here"></a></p>

<p>As you see, the first one has a bigger number in the <em>"key_len"</em> column. And the second one has a bigger number in the <em>"rows"</em> column.</p>

<p>I want to know, which one is more efficient ?</p>

<p><strong>Note:</strong> My dataset is pretty small.</p>