I have already created a web application based on a graph database. I am wondering if there is a possibility to convert the graph database into a relational database.
Thank you in advance.
I'll assume you are using Neo4j since your question has the Neo4j tag.
If you are wanting to export data from Neo4j into a relational database you might want to consider using CSV files as an intermediate step as many relational databases have CSV import tooling. I've used the neo4j-shell tools extension for this purpose in the past. Also, here is a recent blog post about exporting data from Neo4j to CSV format.