The fact that the data owners outsource their data to external service providers introduces many security and privacy issues. Among them, the most significant research questions relate to data confidentiality and user privacy. Encryption was regarded as a solution for data confidentiality. The privacy of a user is characterized by the query he poses to the server and its result. We explore the techniques to execute the SQL query over the encrypted data without revealing to the server any information about the query such as the query type or the query pattern, and its result. By implementing all the relational operators by using the unique selection operator on the server-side database with a constant number of elements in each time of selection, our proposal can defeat against the statistical attacks of the untrusted server compromising data confidentiality and user privacy. Experimental evaluation demonstrates that our proposal less affects the system’s performance and is applicable in the real world.