Question

我在使用外键从父表中重新获取值时遇到了问题。

我正在使用两张桌子，

1）问题表

2）答案表

在问题表字段中，questionId，question和requiredTime。在答案表字段中，answerId，answer和questionId（从问题表中引用的外键）

我的问题是，在问题表中如何获取questionId的值并插入Answer表？

对于一个问题有4个答案意味着4个选项按照问题。

//Create Table Question
    public static final String CREATE_QUESTION = "CREATE TABLE IF NOT EXISTS "
            + TABLE_QUESTION
            + " ( "
            + KEY_QUESTION_ID
            + " INTEGER primary key not null , "
            + KEY_QUESTION
            + " text not null , "
            + KEY_TIME_REQUIRED + " text " + ");";


   //Create Table Answer
    public static final String CREATE_ANSWER = "CREATE TABLE IF NOT EXISTS "
            + TABLE_ANSWER
            + " ( "
            + KEY_ANSWER_ID
            + " INTEGER primary key not null , "
            + KEY_ANSWER
            + " text , "
            + KEY_QUESTION_ID
            + " INTEGER ,"
            + " FOREIGN KEY (" + KEY_QUESTION_ID + ") REFERENCES " + TABLE_QUESTION + " (" + KEY_QUESTION_ID + "));";


In Code,

                    for (int i = 0; i < arr_question_id.size(); i++) {

                            item_bean.setTimeRequired(arr_time_required.get(i));
                            item_bean.setQuestionId(arr_question_id.get(i));
                            item_bean.setQuestion(arr_question.get(i));

                            dbAdapter.openForWrite();
                            dbAdapter.insertQuestion(Integer.parseInt(arr_question_id.get(i)), arr_question.get(i), arr_time_required.get(i));
                            dbAdapter.close();
                        }


                        for (int j = 0; j < arr_answer_id.size(); j++) {
                            item_bean.setAnswerId(arr_answer_id.get(j));
                            item_bean.setAnswer(arr_answer.get(j));
                            item_bean.setCorrect(arr_correct.get(j));

                            System.out.println("!!!!!!!!!!1 Integer.parseInt(arr_question_id.get(j)=====" + json_object_question.getString("questionID"));

                            dbAdapter.openForWrite();
                            dbAdapter.insertAnswer(Integer.parseInt(arr_answer_id.get(j)), arr_answer.get(j), Integer.parseInt(json_object_question.getString("questionID")));
                            dbAdapter.close();
                        }

Problem with below Line,
 dbAdapter.insertAnswer(Integer.parseInt(arr_answer_id.get(j)), arr_answer.get(j), Integer.parseInt(json_object_question.getString("questionID")));

For Question Id,For one Question loop repeat 4 times.


Table Question
***************
questionId  question                    timeRequired
1           What is your Name?          10
2           What is your pets Name?     10
3           What is your native?        10  
etc.

Table Answer
***********
answerId       answer       questionId
101            Neha         1
102            Sneha        1
103            Meeta        1
104            Mamata       1

105            Meetu        2
106            Keenu        2
107            Teenu        2
108            Nehu         2

etc.

我无法为Table Answer获取questionId的值。请帮我。我在等你的回复和你的建议。请建议我。谢谢。里纳

Answer 1

你几乎已经完成了所有事情，只需要从你的答案表中选择你想要的问题ID：

SQLiteDatabase db = this.getWritableDatabase();

String[] columns = new String[] { "answer" }    
String where = KEY_QUESTION_ID + " = ?";
String[] whereArgs = new String[] { questionId + "" };

Cursor c = db.query(
    TABLE_ANSWER /* table */,
    columns /* columns */,
    where /* where or selection */,
    whereArgs /* selectionArgs i.e. value to replace ? */,
    null /* groupBy */,
    null /* having */,
    null /* orderBy */
);

Answer 2

您可以使用联接或创建视图获得所需的结果。这取决于你的需要。 http://www.tutorialspoint.com/sqlite/sqlite_using_joins.htm

你应该保留外键约束，否则没有意义，如果没有问题你会回答为什么？

如何在android中使用外键从父表中获取值？

2 个答案: