Why INNER JOIN self while you can do without?

$query[] = 'SELECT DISTINCT c.*,';
if ($behavior == 'category' && $categoryId) {
$query[] = '0 as `featured`';
$query[] = 'FROM ' . $db->quoteName('#__easyblog_category') . ' AS a';
$query[] = 'INNER JOIN ' . $db->quoteName('#__easyblog_category') . ' AS a1';
$query[] = 'ON a.' . $db->quoteName('id') . ' = a1.' . $db->quoteName('id') . ' AND a1.' . $db->quoteName('id') . ' = ' . $db->Quote($categoryId);
$query[] = 'INNER JOIN ' . $db->quoteName('#__easyblog_post') . ' AS c';
$query[] = 'ON a1.' . $db->quoteName('id') . ' = c.' . $db->quoteName('category_id');


$query[] = 'WHERE c.' . $db->quoteName('id') . '!=' . $db->Quote($id);
}


I am trying to understand the code above, which is part of a query building function. It is used to find related posts of a certain post by select all posts in the post's category except the post itself.

I don't understand why the code above inner joins the category table itself. Shouldn't this be working already?

$query[] = 'SELECT DISTINCT c.*,';
if ($behavior == 'category' && $categoryId) {
//change
$query[] = '0 as `featured`';
$query[] = 'FROM ' . $db->quoteName('#__easyblog_category') . ' AS a';
$query[] = 'INNER JOIN ' . $db->quoteName('#__easyblog_post') . ' AS c';
$query[] = 'ON a.' . $db->quoteName('id') . ' = c.' . $db->quoteName('category_id');


$query[] = 'WHERE c.' . $db->quoteName('id') . '!=' . $db->Quote($id);
}

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