What is the method for sharding databases and tables in MyBatis?

MyBatis itself does not provide official support for sharding databases and tables, but it can be achieved using the following methods:

1. Generate entity classes and Mapper interfaces with MyBatis Generator: According to the sharding rules, generate corresponding entity classes and Mapper interfaces, and define corresponding SQL statements in the Mapper interfaces.
2. Utilizing partitioned tables in databases: Some databases, like MySQL and Oracle, offer the option of using partitioned tables. By creating partitioned tables in the database, data can be stored in different partitions, achieving the effect of splitting tables. In MyBatis, dynamic SQL statements can be used to select which partition to operate on based on the partitioning rules.
3. By utilizing database sharding middleware, such as Sharding-JDBC and MyCAT, which are open source solutions for sharding databases and tables, a middleware layer can be inserted between the application and the database to store data across multiple databases and tables based on sharding rules. In MyBatis, this can be achieved by configuring the SQL statements in Mapper interfaces to use the data source provided by the middleware.

It is important to consider data consistency and transaction handling when performing database sharding. Sharding may lead to issues with cross-database transactions, thus requiring the use of a distributed transaction framework for resolution.