ABSTRACT
The knowledge of database is more and more important with the development of network information. It is important of query to operate database. Users always apply the query not only one table or more tables but also simple query or complicated query including subquery. A lot of dates with hierarchical structure are in practical application, such as enterprise ERP (Enterprise Resource Planning), PDM (Product Data Management) and so on. However users ignore the hierarchical query with the nature of tree usually, so the paper focuses on the analysis and applications of it.
