How do database studies generally differ from randomized controlled clinical trials?

Database studies and randomized controlled clinical trials differ primarily in their methodology and purpose. Database studies utilize existing data from electronic health records or other sources, whereas randomized controlled trials involve the collection of new data through a controlled experiment. This can make database studies generally less expensive and shorter in duration compared to clinical trials. Additionally, database studies often focus on larger populations, while clinical trials may involve more focused research on a single patient or small group. While options A and B may seem plausible, they do not address the fundamental difference in methodology between database studies and clinical trials. Option D is incorrect because clinical trials typically involve a larger population, rather than focusing on a single patient.