How to solve the issue of missing bound variables in MyBatis?

If there is an issue of missing bound variables in MyBatis, you can try the following solutions:

1. Verify that the variable names in the SQL statement are correct: make sure the variable names used in the SQL statement match those defined in the mapping file or annotations.
2. Check if the variable type is correct: make sure the variable type matches the corresponding column type in the database. For example, if the column type in the database is a string and the variable type is an integer, it will result in an error of binding non-existing variables.
3. Check if the parameter mapping in the mapping file or annotation is correct: Ensure that the name, type, and position of the parameter mapping match the placeholders in the SQL statement.
4. Check for the use of dynamic SQL statements: if dynamic SQL statements are being used (such as if, choose, foreach tags), make sure that all possible branches have correct parameter mappings.
5. Check for syntax errors: If there are errors in the SQL statement, it may cause issues with missing bound variables. Use a database client tool to execute the SQL statement and verify the syntax is correct.

If the above methods do not solve the issue, consider turning on MyBatis logging to review the specific error message in order to better pinpoint and resolve the problem.