(Drupal 7) Create a table in a database other than the default during module installation. Database must already be specified in settings.php. Original source: http://drupal.stackexchange.com/a/51673/28700

d7module.install

<?php

/**
 * @file
 * Install, update and uninstall functions for the d7module module.
 */

function d7module_schema_shared() {
  $schema['mytable'] = array(
    'description' => 'My table description.',
    'fields' => array(
      'myfield' => array(
        'description' => 'My field description.',
        'type' => 'serial',
        'size' => 'medium',
        'not null' => TRUE,
        'unsigned' => TRUE,
      ),
    ),
    'primary key' => array('myfield'),
  );
  return $schema;
}

/**
 * Implements hook_install().
 */
function d7module_install() {
  db_set_active('otherdb');
  $schema = d7module_schema_shared();
  foreach ($schema as $name => $table) {
    db_create_table($name, $table);
  }
  db_set_active();
}

/**
 * Implements hook_uninstall().
 */
function d7module_uninstall() {
  db_set_active('otherdb');
  $schema = d7module_schema_shared();
  foreach ($schema as $name => $table) {
    db_drop_table($name);
  }
  db_set_active();
}