Question

我已经在Stackoverflow中看到了这个问题，但是我无法得到想要的东西我有两张桌子，教师和学生

$(".list").on('click', function() {
    if ($(this).hasClass('ani')) {
        $(this).removeClass("ani");
    }
    else {
        $('.list').removeClass("ani");
        $(this).addClass("ani");
    }
});

现在，我想同时匹配学生和教职员工，并显示在Recyclerview上，但我无法做到。

简介：- 我正在制作一个出勤应用程序，当老师进入教室时而出勤时间该应用程序将仅显示正在学习特定学科的学生，我的意思是假设我是老师并且我只教英语，所以我教室里的学生都是英语学习学生与我使用用户名和密码登录时在应用程序中想要的相同它将显示“我的姓名”和“我教的科目”，以及仅想学习英语科目的学生名单，那么该怎么做呢？我希望你明白我想说的话。

这是我到目前为止完成的代码

DBHELPER.JAVA

in Faculty table:-
user_id
user_name
user_subject

in Student Table:-
student_id
student_name
student_subject

FacultyActivity.Java（我必须在其中显示学生列表）

private static final int DATABASE_VERSION = 1;

// Database Name
private static final String DATABASE_NAME = "AttendanceManager.db";

// User table name
private static final String TABLE_USER = "user";

// User Table Columns names
public static final String COLUMN_USER_ID = "user_id";
public static final String COLUMN_USER_NAME = "user_name";
public static final String COLUMN_USER_SUBJECT = "user_subject";
private static final String COLUMN_USER_EMAIL = "user_email";
private static final String COLUMN_USER_PASSWORD = "user_password";


// create table sql query
private String CREATE_USER_TABLE = "CREATE TABLE " + TABLE_USER + "("
        + COLUMN_USER_ID + " INTEGER PRIMARY KEY AUTOINCREMENT,"
        + COLUMN_USER_NAME + " TEXT,"
        + COLUMN_USER_SUBJECT + " TEXT,"
        + COLUMN_USER_EMAIL + " TEXT,"
        + COLUMN_USER_PASSWORD + " TEXT"
        + ")";

// drop table sql query
private String DROP_USER_TABLE = "DROP TABLE IF EXISTS " + TABLE_USER;


// User table name
private static final String TABLE_STUDENT = "student";

// User Table Columns names
private static final String COLUMN_STUDENT_ID = "student_id";
private static final String COLUMN_STUDENT_NAME = "student_name";
private static final String COLUMN_STUDENT_SUBJECT = "student_subject";
private static final String COLUMN_STUDENT_EMAIL = "student_email";
private static final String COLUMN_STUDENT_PASSWORD = "student_password";


// create table sql query
private String CREATE_STUDENT_TABLE = "CREATE TABLE " + TABLE_STUDENT + "("
        + COLUMN_STUDENT_ID + " INTEGER PRIMARY KEY AUTOINCREMENT,"
        + COLUMN_STUDENT_NAME + " TEXT,"
        + COLUMN_STUDENT_SUBJECT + " TEXT,"
        + COLUMN_STUDENT_EMAIL + " TEXT,"
        + COLUMN_STUDENT_PASSWORD + " TEXT"
        + ")";
// drop table sql query
private String DROP_STUDENT_TABLE = "DROP TABLE IF EXISTS " + TABLE_STUDENT;

public DatabaseHelper(Context context) {
    super(context, DATABASE_NAME, null, DATABASE_VERSION);
}

@Override
public void onCreate(SQLiteDatabase sqLiteDatabase) {
    sqLiteDatabase.execSQL(CREATE_USER_TABLE);
    sqLiteDatabase.execSQL(CREATE_STUDENT_TABLE);
}

@Override
public void onUpgrade(SQLiteDatabase sqLiteDatabase, int i, int i1) {
    sqLiteDatabase.execSQL(DROP_USER_TABLE);
    sqLiteDatabase.execSQL(DROP_STUDENT_TABLE);
    onCreate(sqLiteDatabase);
}
    public List<Student> getStdsubjectss() {


    List<Student> userList = new ArrayList<Student>();

    String rawQuery = " SELECT " + COLUMN_STUDENT_ID + " , "
            + COLUMN_STUDENT_NAME + " , " + COLUMN_STUDENT_SUBJECT + " , "
            + COLUMN_STUDENT_EMAIL + " , " + COLUMN_USER_SUBJECT + " FROM "
            + TABLE_STUDENT + " std, " + TABLE_USER + " fact WHERE std."
            + COLUMN_STUDENT_SUBJECT + " = fact." + COLUMN_USER_SUBJECT;

    String sql = "SELECT student.student_id,student.student_name,student.student_subject,student.student_email,user.user_subject FROM student, " +
            "user WHERE student.student_subject = '**What should i Add here to make it work??**' " ;

    Log.e("QUERY", sql);
    SQLiteDatabase db = this.getReadableDatabase();

    Cursor cursor = db.rawQuery(sql, null);

    if (cursor.moveToFirst()) {
        do {
            Student student = new Student();
            student.setId(Integer.parseInt(cursor.getString(cursor.getColumnIndex(COLUMN_STUDENT_ID))));
            student.setName(cursor.getString(cursor.getColumnIndex(COLUMN_STUDENT_NAME)));
            student.setSubject(cursor.getString(cursor.getColumnIndex(COLUMN_STUDENT_SUBJECT)));
            student.setEmail(cursor.getString(cursor.getColumnIndex(COLUMN_STUDENT_EMAIL)));
            Faculty department = new Faculty();
            department.setSubject(cursor.getString(cursor.getColumnIndex(COLUMN_USER_SUBJECT)));
            userList.add(student);
        } while (cursor.moveToNext());

    }
    cursor.close();
    db.close();

    return userList;

}

我已经在sqli字符串中标记了应该在其中添加什么以使代码具有动态性，如果我只是放置

AppCompatTextView facterName,facterSubj;

RecyclerView recyclerViewStudents;
List<Student> studentList;
StudentRecyclerAdapter studentRecyclerAdapter;
DatabaseHelper databaseHelper;
SQLiteDatabase sqLiteDatabase;
Student student;
Faculty faculty;
@Override
protected void onCreate(Bundle savedInstanceState) {
    super.onCreate(savedInstanceState);
    setContentView(R.layout.activity_faculty);

    facterName = findViewById(R.id.factersNamer);
    facterSubj = findViewById(R.id.factersSubj);
    recyclerViewStudents = findViewById(R.id.recyclerViewStudents);
    Intent intent = getIntent();
    String name = intent.getStringExtra("username");
     databaseHelper = new DatabaseHelper(getApplicationContext());

     studentList = new ArrayList<>();
    studentRecyclerAdapter = new StudentRecyclerAdapter(studentList);

    RecyclerView.LayoutManager mLayoutManager = new LinearLayoutManager(getApplicationContext());
    recyclerViewStudents.setLayoutManager(mLayoutManager);
    recyclerViewStudents.setItemAnimator(new DefaultItemAnimator());
    recyclerViewStudents.setHasFixedSize(true);
    recyclerViewStudents.setAdapter(studentRecyclerAdapter);
    databaseHelper = new DatabaseHelper(this);
    getDataFromSQLite();

}

@SuppressLint("StaticFieldLeak")
private void getDataFromSQLite() {
    // AsyncTask is used that SQLite operation not blocks the UI Thread.
    new AsyncTask<Void, Void, Void>() {
        @Override
        protected Void doInBackground(Void... params) {
            studentList.clear();
            studentList.addAll(databaseHelper.getStdsubjectss());
            return null;
        }

        @Override
        protected void onPostExecute(Void aVoid) {
            super.onPostExecute(aVoid);
            studentRecyclerAdapter.notifyDataSetChanged();
        }
    }.execute();

}

我显示所有具有英语科目的学生但显示两次时间

 String sql = "SELECT student.student_id,student.student_name,student.student_subject,student.student_email,user.user_subject FROM student, " +
        "user WHERE student.student_subject = 'English' " ;

这是我面临的问题但是现在我的主要问题是制作动态sqlite。

帮帮我谢谢

Answer 1

使用LEFT JOIN连接两个表的行。

有关JOIN的更多信息，请参见下面的链接： LEFT JOIN

在您的情况下：

String sql = "SELECT student.student_id,student.student_name,student.student_subject,student.student_email,user.user_subject FROM student, " +
        "LEFT JOIN user ON student.student_subject = user.user_subject WHERE student.student_subject = 'English'  " ;

如何匹配来自多个表的两行？

1 个答案: