Question

尝试在MySQL中的数据表中添加新记录失败，并显示错误消息：

无法添加或更新子行

我可以在xampp中手动执行相同的命令，它可以正常工作，但是在我的应用程序下运行时却不能。这是代码，从表“ users”开始，然后是“ transactions”

 public void CreateUsersTable(){
    try {
        String SQL = "CREATE TABLE IF NOT EXISTS Users ("
                + "Username varchar(80) NOT NULL,"
                + "Userpassword varchar(80) ,"
                + "User_GSM VARCHAR(30),"
                + "User_Tel_Home VARCHAR(30),"
                + "User_Address Varchar(100), "
                + "User_City Varchar(20), "
                + "User_Position Varchar(100), "
                + "PRIMARY KEY(Username))";

        //con = DBModule.ConnectDataBase.ConnectDataBase_Method();
        statement = con.prepareStatement(SQL);
        statement.executeUpdate();

    } catch (SQLException ex) {
         CustomControls.CustomTools.CustomMsgBox(ex.getMessage());
    }
}

和第二张表

  public void CreateTransactionsTable(){
    try {
        String SQL = "CREATE TABLE IF NOT EXISTS Transactions ("
                + "TransactionsNum INT(18) NOT NULL AUTO_INCREMENT,"
                + "TransactionsDate DATE,"
                + "TransactionsAmount float(8), "
                + "TransactionsUsername varchar(80) ,"
                + "PRIMARY KEY(TransactionsNum) , "
                + "FOREIGN KEY(TransactionsUsername) REFERENCES Users(Username) )"; // foregign key is the key in this table to accessed from main calling

        //con = DBModule.ConnectDataBase.ConnectDataBase_Method();
        statement = con.prepareStatement(SQL);
        statement.executeUpdate();
    } catch (SQLException ex) {
          CustomControls.CustomTools.CustomMsgBox(ex.getMessage());
    }
}

最后，这是更新数据库的语句

 String addTRansSQL = "insert into transactions ( TransactionsDate , TransactionsAmount , TransactionsUsername ) " 
            + " values( '" + sqlDate + "' , '" + tramount + "' , ' " + loggeduser + "' )";

Answer 1

简而言之，您要尝试添加与用户表中不存在的用户的交易行，请尝试以下行“ SET FOREIGN_KEY_CHECKS = 0”

无法添加或更新表

1 个答案: