如何用光标搜索数据库中的long类型

Question

我想在将数据添加到表之前确定studentId与另一个studentId不一样但我不知道如何使用光标搜索长类型

我的代码：

    public void SaveStudent(Long studentId , int classID , String studentName)
{
    String stdId = studentId.toString();
    Cursor cursor = database.rawQuery("select * from student where student_id = ?",
                                        new String[]{stdId});

    if (cursor.getCount() == 0)
    {
        ContentValues values = new ContentValues();

        values.put("student_id", studentId);
        values.put("class_id", classID);
        values.put("student_name", studentName);

        database.insert("student", null, values);

        Toast.makeText(context, "save!", Toast.LENGTH_SHORT).show();
    }
    else
    {
        Toast.makeText(context, "StudentID is duplicate", Toast.LENGTH_SHORT).show();
    }
}

logcat错误：

02-23 21:37:39.108 26986-26986/com.example.user.classmanager E/SQLiteLog: (1) near "=": syntax error
02-23 21:37:39.110 26986-26986/com.example.user.classmanager E/AndroidRuntime: FATAL EXCEPTION: main
      Process: com.example.user.classmanager, PID: 26986
          android.database.sqlite.SQLiteException: near "=": syntax error (code 1): ,           while compiling: select * from studentwhere student_id = ?
          at android.database.sqlite.SQLiteConnection.nativePrepareStatement(Native Method)
          at android.database.sqlite.SQLiteConnection.acquirePreparedStatement(SQLiteConnection.java:887)
          at com.example.user.classmanager.DatabaseHandler.SaveStudent(DatabaseHandler.java:184)
          at com.example.user.classmanager.SecondTab$1$1$1.onClick(SecondTab.java:97)

Answer 1

尝试以下

    Cursor cursor = database.rawQuery("select * from student where student_id = ?",
                                            new String[]{String.valueOf(stdId)});