With the development of blockchain, blockchain has a broad prospect as a new type of data management system. However, limited to the data modeling method of blockchain, the usability of blockchain is restricted; In addition, every blockchain system has its own native but naive interfaces, when developing based on the different blockchain systems, which will leads to low development efficiency and high development costs. In this study, we construct a SQL-Middleware for blockchain system to solve these problems. The SQL-Middleware first performs relational modeling of blockchain data, mapping the blockchain data into a relational table; On the basis of modeling the blockchain data, SQL-Middleware encapsulates a set of SQL interfaces for blockchain system, thus realizing the unification of interface access methods of different blockchain systems. At last, we implement the SQL-Middleware based on the open source blockchain system CITA. Demonstration shows that the SQL-Middleware greatly improves the data management capabilities of blockchain and simplifies the blockchain access steps.
