The clinical database keeps records on patients; the data is collected during the regular day-to-day events of the hospital. This data may be used for financial reporting, management, or for monitoring and evaluation. Due to the existing system, there are several problems that includes: the monitoring of the impact of specific disease such as diabetes mellitus is very difficult, also the study of the effect of medical processes is very difficult, and moreover, for a hospital in an academic environment, with this situation, physicians and researcher's time is wasted by having to collect information that may be used to discover the relationships between different diseases such as the relationship between DM and other diseases. The objective of this book is to develop a Clinical Data Warehousing for analyzing diabetic patient's data. On Line Analytical Processing used as a method of analysis, it represents the data in terms of cube and the user or analyst can rotate this cube to see it from different side and this help in making decision in an effective way.