Hi Michael,

As the custom posts/fields, are a part of the WordPress database;

pulling this data can only be done through MySQL query-based tables.

Please note: Using this plugin feature requires at least a basic knowledge of SQL. It is assumed that you can create the table in some MySQL data manager (e.g., PHPMyAdmin, MySQL Workbench), and prepare a SQL query that will return the data you need. 

A good way to achieve this can be experimenting using our WPDB SQL Query Constructor tool.

You can also try this other SQL Query helper Tool,

Create a MySQL-query-based table by querying a database,

that one has a wider range of all tables you can choose from your Database outside of WPDB.

- Please note: this tool is not an ultimate query generator. It simply constructs a suggestion of a query. We are constantly working to improve it, but SQL is such a complicated and flexible language that full automation for constructing queries is next to impossible. 

Consequently, the more complicated the query, the higher is the probability that it will not return exactly what you need. So, you will often need to play around with the resulting query.

Please be advised that writing custom SQL Queries or debugging Queries does not fall under what our support covers.

You can check out this official page of WP codex,  for help with writing custom Queries.