java - 如果不存在记录，如何创建一个删除表的事件和另一个事件

Question

我正在创建一个总线表，其中包含一个事件来维护数据。如果总线表中不存在记录，是否可以通过 DropBusEvent 事件删除表和 autoDelete 事件？

        stt.execute("CREATE TABLE IF NOT EXISTS bus"
                + "(id INT(11) NOT NULL AUTO_INCREMENT PRIMARY KEY,"
                + "mac VARCHAR(30) NOT NULL UNIQUE,"
                + "route int(11) NOT NULL,"
                + "latitude FLOAT(10,6) NOT NULL,"
                + "longitude FLOAT(10,6) NOT NULL,"
                + "created_at TIMESTAMP DEFAULT CURRENT_TIMESTAMP)");

        stt.execute("CREATE EVENT IF NOT EXISTS  AutoDelete "
                + "ON SCHEDULE EVERY 3 MINUTE "
                + "DO "
                + "DELETE FROM bus WHERE created_at < (NOW() - INTERVAL 3 MINUTE)");

        // I tried this statement here but it does not work.
        stt.execute("CREATE EVENT IF NOT EXITS DropBusTable "
                + "Do "
                + "DROP TABLES IF EXISTS bus");

我收到您的 SQL 语法有错误；检查与您的 MySQL 服务器版本相对应的手册，了解在第 1 行的“EXITS DropBusTableDROP TABLES IF EXISTS bus”附近使用的正确语法


Answer 1

您的语法有错误:

EXITS 而不是 EXISTS在行中

stt.execute("CREATE EVENT IF NOT EXITS DropBusTable "