With the advent of object-oriented database systems there is a need to migrate/integrate old systems, mainly relational ones, to/into object-oriented systems. In this paper we propose a method to automatically translate SQL queries to OQL ones. The method is based on a graph representation of SQL queries. This graph is enriched and transformed in a series of stages which take into account the caracteristics of the object schema with respect to the relational one (new entity type, ISA relationship, class hierarchy, etc.). This semantic enrichment allows an optimized translation of the SQL queries compared with a purely syntaxic translation.