What is my error trying to create a new table in the database?

That’s not how you create tables with dbDelta. dbDelta expects an SQL statement as its argument, but the code in your question passes none. What’s more, the SQL is passed into wpdb->query, and has no checks or sanitisation. A quick run of PHPCS would reveal warnings that no prepare call is used.

Instead, the official documentation at https://developer.wordpress.org/reference/functions/dbdelta/ has this example:

global $wpdb;
$table_name = $wpdb->prefix . 'dbdelta_test_001';
$wpdb_collate = $wpdb->collate;
$sql =
"CREATE TABLE {$table_name} (
    id mediumint(8) unsigned NOT NULL auto_increment ,
    first varchar(255) NULL,
    PRIMARY KEY  (id),
    KEY first (first)
    )
    COLLATE {$wpdb_collate}";
 
require_once(ABSPATH . 'wp-admin/includes/upgrade.php');
dbDelta( $sql );

Note however, that dbDelta has extremely specific formatting requirements. For example, there must be 2 spaces after PRIMARY KEY. dbDelta will also adjust existing tables to match the statement, and it will create the table if it doesn’t exist

Also keep in mind that in a lot of cases custom post types are easier and more performant. In this case, a CPT + taxonomy might be more performant in some circumstances due to the absence of indexes on the custom tables, and the loss of the internal WP_Cache system

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