There had been several efforts for efficient translation from SPARQL into SQL. The R2RML standard provides an ability to view existing relational data in the RDF data model and offer a virtual SPARQL endpoint over the mapped relational data. However, R2RML does not support flexible mapping when database schema change frequently. This paper presents an efficient translation technique from SPARQL into SQL to manage database schema changes by extending R2RML. The authors applied it to a tag metadata catalog service, and it demonstrated the effectiveness of their method.