In this paper, we propose a novel relational database watermarking algorithm for joint ownership. We offer a technique to break the main secret into multiple parts and hide them individually in a relational database. The whole algorithms are given in detailed. The (k, n) threshold scheme is used to decide the minimum number of parts required to recover the secret data completely. Through deep data analysis, experimental results show how the proposed scheme can offer robust mechanism to protect data loss especially for the tuples deleting.