The reader deletion function of the book management system based on Java shows that the database update failed every time it runs. Ask the boss for help?
The easiest way is to solve the problem through debugging. I read your code. If this is the only prompt message, I suspect that the id you passed is wrong, resulting in the deletion of 0 records, and it is judged as a failure to delete, or the number of deleted records is greater than 1, and it is judged as a failure to delete. The specific situation still needs to be analyzed by debugging the code.