With the ongoing implementation of electronic medical records, more and more clinical data are being recorded in a digital format, often as free text. Analyzing data in free text format is inefficient, prone to error, and difficult. While mapping free text to coded concepts can address some of these issues, additional structure is necessary to enable non-expert end users to retrieve data from a clinical warehouse. A review of the current literature reveals that this structure is often built and maintained locally with significant effort. Alternatively, one can use external reference terminology to provide the necessary structure. This study examined whether one such reference terminology, SNOMED Clinical terms could enhance the querying of a clinical data warehouse.