java - JDBC计算平均值

Question

这是我的数据库表，名为 Cruise_Serial: enter image description here

我想获取每个cruiseID的总平均评价数，例如:

对于 CruiseID 4013，它必须是:(5+5+4+4+3+4+4+5+4+4+4+4)/12这是我为PreparedStatement 编写的内容:

PreparedStatement ps = connect1.prepareStatement("SELECT CRUISE_SERIAL＿NUMBER, AVG(CRUISE_SERIAL.EVALUATION_FOOD, CRUISE_SERIAL.EVALUATION_SEHEDULE, CRUISE_SERIAL.EVALUATIONA_COMFORTABLE,CRUISE_SERIAL.EVALUATION_TIDY),AVG(CRUISE_SERIAL_NUMBER) "
          + "FROM CRUISE_SERIAL GROUP by CRUISE_SERIAL_NUMBER");

但是我的这行代码中显示了错误，请帮助我如何修复它。谢谢!!

Exception in thread "main" java.sql.SQLSyntaxErrorException: Lexical error at line 1, column 21.  Encountered: "\uff3f" (65343), after : "".
    at org.apache.derby.client.am.SQLExceptionFactory.getSQLException(Unknown Source)
    at org.apache.derby.client.am.SqlException.getSQLException(Unknown Source)
    at org.apache.derby.client.am.ClientConnection.prepareStatement(Unknown Source)
    at lab.User_Cruise.cruiseEvaluation

Answer 1

您的某些下划线不是常规下划线，请参阅此处的第二个下划线:

CRUISE_SERIAL＿NUMBER

正如错误告诉您的那样，这个大下划线是unicode字符U+FF3F，即

FULLWIDTH LOW LINE

只需将其替换为常规下划线即可。