regexp to find after 4th occurrence

Question

I using REGEXP in wp_query. I am storing post meta as 20181020 (yyyymmdd) so basically I want a REGEXP so that I can filter if user enter 10 (mm) in filter box

currently I am using this '^'.$date but this only works if user entered yyyymm format. I want to search this if use enter value in either yyyy or mm there is no need for dd.

I want to filter based on user input.

User will select month or year, for example, if user select Dec month then i will get response 10. Then i pass this value in meta_query. here is the meta query. But in this issue is data stored in post meta is in yyyymmdd format. So I want a regexp where I can query to 4th occurrence.

$args = array(
        'post_type' => 'achievements',
        'posts_per_page' => -1,
        'post_status' => 'publish',
    'meta_query' => array(
        array(
        'key' => 'achievement_date',
        'value' => '^'.$date,
        'compare' => 'REGEXP'
        )
    )
    );
    $the_query = new WP_Query( $args );

Answer 1

I figured it out. i just need to use this ^.... expression. This will skip first 4 characters.