Wenn man eine Magento Datenbank via phpMyAdmin einspielen will, muss man die "foreign key constraints" vorübergehend deaktivieren:

An den Anfang der .sql-Datei stellen:

SET @OLD_CHARACTER_SET_CLIENT=@@CHARACTER_SET_CLIENT;
SET @OLD_CHARACTER_SET_RESULTS=@@CHARACTER_SET_RESULTS;
SET @OLD_COLLATION_CONNECTION=@@COLLATION_CONNECTION;
SET NAMES utf8;
SET @OLD_UNIQUE_CHECKS=@@UNIQUE_CHECKS, UNIQUE_CHECKS=0;
SET @OLD_FOREIGN_KEY_CHECKS=@@FOREIGN_KEY_CHECKS, FOREIGN_KEY_CHECKS=0;
SET @OLD_SQL_MODE=@@SQL_MODE, SQL_MODE='NO_AUTO_VALUE_ON_ZERO';
SET @OLD_SQL_NOTES=@@SQL_NOTES, SQL_NOTES=0;

An das Ende der .sql-Datei stellen:

SET SQL_MODE=@OLD_SQL_MODE;
SET FOREIGN_KEY_CHECKS=@OLD_FOREIGN_KEY_CHECKS;
SET UNIQUE_CHECKS=@OLD_UNIQUE_CHECKS;
SET CHARACTER_SET_CLIENT=@OLD_CHARACTER_SET_CLIENT;
SET CHARACTER_SET_RESULTS=@OLD_CHARACTER_SET_RESULTS;
SET COLLATION_CONNECTION=@OLD_COLLATION_CONNECTION;
SET SQL_NOTES=@OLD_SQL_NOTES;

Quelle: www.imagedia.com/2009/10/how-to-restore-data-in-magento-from-a-backup