Abstract: A computer-implemented method of guiding a user during the construction of a search query to locate an item of interest in a database, wherein a search index of the database is a hierarchical data structure that includes at least one aspect of items with the aspect having facets. The method includes receiving a search query from a user, building a search expression data structure according to the search query, expanding the search expression data structure to determine the results for at least one facet available to refine the user's search query and presenting a representation of the results of the user's search query along with the result for the at least one facet to the user, thus providing guidance to the user for development of the search query regarding the existence of valid results. The method is useful to avoid incorrect or NULL results.