WPDB SQL query SELECT from category

If you are find products by specified category. Please find below code :

$results = $wpdb->get_col( "
    SELECT p.ID
    FROM {$wpdb->prefix}posts as p
    INNER JOIN {$wpdb->prefix}postmeta as pm ON p.ID = pm.post_id
    LEFT JOIN {$wpdb->prefix}term_relationships ON ({$wpdb->prefix}posts.ID = {$wpdb->prefix}term_relationships.object_id) 
    WHERE p.post_type LIKE 'product'
    AND p.post_status LIKE 'publish'
    AND pm.meta_key LIKE '_stock_status'
    AND pm.meta_value LIKE 'instock' 
    AND {$wpdb->prefix}term_relationships.term_taxonomy_id IN ( 'cat 1', 'cat 2', 'cat 3' ) 
" );

Note : You need to replace “cat 1”, “cat 2” and “cat 3” with your category.