In database-as-a-service (DAS) paradigm, data owners delegate their data to a third-party: Database service provider (DSP). Compared with traditional DBMS, DAS provides Web-based data access to relieve heavy database management routines. To guarantee quality of database service, most previous work has focus on data privacy and data integrity. This paper focuses on authentication of data integrity. All previous approaches for data integrity authentication require the DSP either to provide extra information or to store extra data. In dynamic scenario, the authentication data should be updated correspondingly, which is inefficient to deploy in real life. This paper proposes a data integrity auditing approach based on validating queries. In this approach, validating queries are generated from previous queries sent by the user. According to the result of validating queries and based on the relationship between previous queries and validating queries, the client can achieve the integrity auditing effectively and efficiently based on the probability. Experimental results confirm the effectiveness of the approach.