bp_core_maybe_install_signups()

function bp_core_maybe_install_signups() {
	global $wpdb;

	// The table to run queries against.
	$signups_table = $wpdb->base_prefix . 'signups';

	// Suppress errors because users shouldn't see what happens next.
	$old_suppress  = $wpdb->suppress_errors();

	// Never use bp_core_get_table_prefix() for any global users tables.
	$table_exists  = (bool) $wpdb->get_results( "DESCRIBE {$signups_table};" );

	// Table already exists, so maybe upgrade instead?
	if ( true === $table_exists ) {

		// Look for the 'signup_id' column.
		$column_exists = $wpdb->query( "SHOW COLUMNS FROM {$signups_table} LIKE 'signup_id'" );

		// 'signup_id' column doesn't exist, so run the upgrade
		if ( empty( $column_exists ) ) {
			bp_core_upgrade_signups();
		}

	// Table does not exist, and we are a single site, so install the multisite
	// signups table using WordPress core's database schema.
	} elseif ( ! is_multisite() ) {
		bp_core_install_signups();
	}

	// Restore previous error suppression setting.
	$wpdb->suppress_errors( $old_suppress );
}