how to get post by post id in wordpress db code example

Example 1: wordpress get post id

// Retrieve the ID of the current item in the WordPress Loop.
get_the_ID()

Example 2: wordpress query a post by id

//WordPress: Query a specific post by its post type & ID
//For example, query Case Study with ID #12345

<?php query_posts('post_type=case_studies&p=12345'); ?>
  
/*To determine a post ID, refer to the
URL of the post while editing it:
http://localhost...wp-admin/post.php?post=12345...*/