A growing trend in today’s society is outsourcing large databases to the cloud. This permits to move the management burden from the data owner to external providers, which can make vast and scalable infrastructures available at competitive prices. Since large databases can include sensitive information, effective protection of data confidentiality is a key issue to fully enable data owners to enjoy the benefits of cloud-based solutions. Data encryption and data fragmentation have been proposed as two natural solutions for protecting data confidentiality. However, their adoption does not permit to completely delegate query evaluation at the provider. In this chapter, we illustrate some encryption-based and fragmentation-based solutions for protecting data confidentiality, discussing also how they support query execution.