如何检查MySQL查询中是否存在来自数组的值

Question

I want to check if none of the days exist in custom_tag table of my database but the following code doesn't work. Can someone please tell me what I am doing wrong?

$tag_checker = $wpdb->get_results( "SELECT tag FROM custom_tag" );
$days = array( 'Monday', 'Tuesday', 'Wednesday', 'Thursday', 'Friday', 'Saturday', 'Sunday' );

if( empty( array_intersect( $tag_checker, $days ) ) ) :
// then do something
endif;

Answer 1

$days = array( 'Monday', 'Tuesday', 'Wednesday', 'Thursday', 'Friday', 'Saturday', 'Sunday' );
$tag_checker = $wpdb->get_results( "SELECT tag FROM custom_tag WHERE tag IN ('" .implode("','", $days). "')");


if( empty( $tag_checker ) ) :
    echo 'hello';
endif;