cat and cat

query based on two categories

$tax_query = array(
	'relation' => 'AND',
	array(
		'taxonomy'         => 'category',
		'terms'            => '500',
		'field'            => 'term_id',
		'operator'         => 'AND',
	),
	array(
		'taxonomy'         => 'category',
		'terms'            => '300',
		'field'            => 'term_id',
		'operator'         => 'AND',
	),
);