android.database.sqlite.SQLiteException: near “WHERE”: syntax error (Sqlite code 1)

Question

I would be grateful if anyone could help with this code

android.database.sqlite.SQLiteException: near "WHERE": syntax error (Sqlite code 1): , while compiling: SELECT * FROM WHERE category = 'B', (OS error - 2:No such file or directory)

error from debug

My DbHelper is as following

public class DbHelper extends SQLiteOpenHelper {
    private static final String DATABASE_NAME = "Quiz.db";
    private static final String KEY_ID = "id";
    private static final String KEY_QUES = "question";
    private static final String KEY_ANSWER = "answer"; //correct option
    private static final String KEY_OPTA= "opta"; //option a
    private static final String KEY_OPTB= "optb"; //option b
    private static final String KEY_OPTC= "optc"; //option c
    private static final String KEY_OPTD= "optd"; //option d
    private static final String KEY_CAT="category"; //category
    private static final String TABLE_QUEST1 = "questUnit1";
 
    private SQLiteDatabase dbase;

    public DbHelper(Context context) {
        super(context, DATABASE_NAME, null, 1);
    }

    public DbHelper(Context context, String name, SQLiteDatabase.CursorFactory factory, int version) {
        super(context, DATABASE_NAME, factory, version);
    }

    @Override
    public void onCreate(SQLiteDatabase db) {
        dbase=db;

        String sql1 = "CREATE TABLE IF NOT EXISTS " + TABLE_QUEST1 + " ( "
                + KEY_ID + " INTEGER PRIMARY KEY AUTOINCREMENT, " + KEY_QUES
                + " TEXT, " + KEY_ANSWER+ " TEXT, "+KEY_OPTA +" TEXT, "
                +KEY_OPTB +" TEXT, "+KEY_OPTC+" TEXT, "+KEY_OPTD+" TEXT, "+KEY_CAT+" TEXT)";
        db.execSQL(sql1);
        addQuestionsUnit1();

    }

        private void addQuestionsUnit1() {
            QuestionUnit1 q101 = new QuestionUnit1("What is the decimal equivalent of the binary number 10111","21","23","39","42","23","B");
            this.addQuestionsUnit1(q101);
            QuestionUnit1 q102 = new QuestionUnit1("In order to write on a floppy disk with your IBM PC, you must first","digitize it","format it","compile it","hardware it","format it","B");
            this.addQuestionsUnit1(q102);
    
    QuestionUnit1 q249= new QuestionUnit1("Firewalls are used to protect against","Unauthorized Attacks","Viruses","Fire Attacks","Data Driven Attacks","Unauthorized Attacks","E");
            this.addQuestionsUnit1(q249);
            QuestionUnit1 q250= new QuestionUnit1("The first Digital Computer introduced, was named as ","UNIVAC","EDSAC","ENIAC","MARK-1","MARK-1","E");
            this.addQuestionsUnit1(q250);
    
        }

    public void addQuestionsUnit1(QuestionUnit1 quest) {
        //SQLiteDatabase db = this.getWritableDatabase();
        ContentValues values = new ContentValues();
        values.put(KEY_QUES, quest.getQUESTION1());
        values.put(KEY_ANSWER, quest.getANSWER1());
        values.put(KEY_OPTA, quest.getOPTA1());
        values.put(KEY_OPTB, quest.getOPTB1());
        values.put(KEY_OPTC, quest.getOPTC1());
        values.put(KEY_OPTD, quest.getOPTD1());
        values.put(KEY_CAT,quest.getCATEGORY1());
        // Inserting Row
        dbase.insert(TABLE_QUEST1, null, values);
    }



    @Override
    public void onUpgrade(SQLiteDatabase db, int oldVersion, int newVersion) {

    }

    public List<QuestionUnit1> getAllQuestions1(String tname, String lname)
    {
        List<QuestionUnit1> quesList1 = new ArrayList<QuestionUnit1>();
        String selectQuery1 = "SELECT * FROM " + tname+" WHERE "+KEY_CAT+" = '"+lname+"'";
        dbase=this.getReadableDatabase();
        Cursor cursor = dbase.rawQuery(selectQuery1, null);
        // looping through all rows and adding to list
        if (cursor.moveToFirst()) {
            do {
                QuestionUnit1 quest1 = new QuestionUnit1();
                quest1.setID1(cursor.getInt(0));
                quest1.setQUESTION1(cursor.getString(1));
                quest1.setANSWER1(cursor.getString(2));
                quest1.setOPTA1(cursor.getString(3));
                quest1.setOPTB1(cursor.getString(4));
                quest1.setOPTC1(cursor.getString(5));
                quest1.setOPTD1(cursor.getString(6));
                quesList1.add(quest1);
            } while (cursor.moveToNext());
        }
        return quesList1;
    }// end pubic list
}

the code walks like that a butto to To Exercise Activity

if(position == 2){
                    Intent i= new Intent(getApplicationContext(),Unit1ExerciseActivity.class);
                    i.putExtra("table_name",tableName);
                    i.putExtra("level_name","B");
                    startActivity(i);
                    overridePendingTransition(android.R.anim.slide_in_left,android.R.anim.slide_out_right);
                }

and the code in the exercise Activity is

public class Unit1ExerciseActivity extends AppCompatActivity {
    List<QuestionUnit1> quesList1;
    public int score=0;
    int ctr1=1;
    QuestionUnit1 currentQ1;
    TextView txtQuestion1;
    RadioGroup grp;
    RadioButton rda1, rdb1, rdc1, rdd1;
    Button butNext1;
    Random random1 = new Random();
    ArrayList<Integer> list = new ArrayList<Integer>();
    TextView textViewTime1;
    public ArrayList<String> wrongQuestListUnit1 = new ArrayList<String>();
    public ArrayList<String> selectedAnsUnit1 = new ArrayList<String>();
    public ArrayList<String> actualAnswerUnit1 = new ArrayList<String>();
    int number;
    ProgressBar progressBar;
    int progress = 1;
    String tableName="",catName="";
    TextView qstnNo;
    @Override
    protected void onCreate(Bundle savedInstanceState) {
        super.onCreate(savedInstanceState);
        setContentView(R.layout.unit1_exercise_activity);


        qstnNo = (TextView)findViewById(R.id.qstnNo);

        Intent iin=getIntent();
        Bundle b=iin.getExtras();

        if(b!=null){
            tableName=(String)b.get("table_name");
            catName=(String)b.get("level_name");
            Log.d("Table Name",tableName);
            Log.d("Level Name",catName);
        }
        number=0;
        DbHelper db= new DbHelper(this);
        textViewTime1 = (TextView)findViewById(R.id.textViewTime);
        final CounterClass timer = new CounterClass(1800000, 1000);
        timer.start();

        quesList1=db.getAllQuestions1(tableName,catName);
        for(int i=0;i<50;i++){
            while(true){
                int next = random1.nextInt(50);
                if(!list.contains(next))
                {
                    list.add(next);
                    break;
                }
            }
        }
        currentQ1=quesList1.get(list.get(0));
        txtQuestion1=(TextView)findViewById(R.id.textView1);
        rda1=(RadioButton)findViewById(R.id.radio0);
        rdb1=(RadioButton)findViewById(R.id.radio1);
        rdc1=(RadioButton)findViewById(R.id.radio2);
        rdd1=(RadioButton)findViewById(R.id.radio3);
        butNext1=(Button)findViewById(R.id.button1);
        setQuestionView();
        grp = (RadioGroup) findViewById(R.id.radioGroup1);
        butNext1.setEnabled(false);
        grp.setOnCheckedChangeListener(new RadioGroup.OnCheckedChangeListener() {
            @Override
            public void onCheckedChanged(RadioGroup radioGroup, int i) {
                if(i== R.id.radio0 || i == R.id.radio1 || i==R.id.radio2 || i == R.id.radio3)
                    butNext1.setEnabled(true);
            }
        });
        progressBar = (ProgressBar) findViewById(R.id.progressBar);
        progressBar.setMax(30);
        progressBar.setProgress(1);
        butNext1.setOnClickListener(new View.OnClickListener() {
            @Override
            public void onClick(View v) {
                progress = progress+1;
                progressBar.setProgress(progress);
                RadioButton answer = (RadioButton) findViewById(grp.getCheckedRadioButtonId());
                //Log.d("yourans", currentQ1.getANSWER1() + " " + answer.getText());
                if (currentQ1.getANSWER1().equals(answer.getText())) {
                    score++;
                    //Log.d("score", "Your score" + score1);
                }
                else
                {
                    wrongQuestListUnit1.add(number, currentQ1.getQUESTION1());
                    selectedAnsUnit1.add(number, answer.getText().toString());
                    actualAnswerUnit1.add(number, currentQ1.getANSWER1());
                    number++;
                }
                grp.clearCheck();
                butNext1.setEnabled(false);
                if (ctr1 < 31) {
                    if (ctr1 == 30) {
                        butNext1.setText("End Test");
                    }
                    currentQ1 = quesList1.get(list.get(ctr1));
                    setQuestionView();
                } else {
                    timer.onFinish();
                    timer.cancel();
                }
            }
        });

    }

    public class CounterClass extends CountDownTimer {
        public CounterClass(long millisInFuture, long countDownInterval) {
            super(millisInFuture, countDownInterval);
        }

        @Override
        public void onTick(long millisUntilFinished) {
            long millis = millisUntilFinished;
            String hms = String.format("%02d:%02d",
                    TimeUnit.MILLISECONDS.toMinutes(millis) - TimeUnit.HOURS.toMinutes(TimeUnit.MILLISECONDS.toHours(millis)),
                    TimeUnit.MILLISECONDS.toSeconds(millis) - TimeUnit.MINUTES.toSeconds(TimeUnit.MILLISECONDS.toMinutes(millis)));
            textViewTime1.setText(hms);
        }

        @Override
        public void onFinish() {
            showResult();
        }
    }

    public void showResult(){
        Intent intent = new Intent(Unit1ExerciseActivity.this, ResultActivity.class);
        Bundle b = new Bundle();
        b.putInt("scoreUnit1 ", score);//Your score
        b.putString("section",tableName);//Your table name
        b.putString("category",catName);//Your category name
        intent.putStringArrayListExtra("wrongQuestions", wrongQuestListUnit1);
        intent.putStringArrayListExtra("selectedAnswer", selectedAnsUnit1);
        intent.putStringArrayListExtra("actualAnswer", actualAnswerUnit1);
        intent.putExtras(b); //Put your score to your next Intent
        startActivity(intent);
        finish();
    }

    private void setQuestionView(){
        txtQuestion1.setText(currentQ1.getQUESTION1());
        rda1.setText(currentQ1.getOPTA1());
        rdb1.setText(currentQ1.getOPTB1());
        rdc1.setText(currentQ1.getOPTC1());
        rdd1.setText(currentQ1.getOPTD1());
        if(ctr1<10)
            qstnNo.setText("0" + ctr1 + "/30");
        else
            qstnNo.setText("" + ctr1+ "/30");
        ctr1++;
    }

    @Override
    public void onBackPressed() {
        //super.onBackPressed();
        AlertDialog.Builder builder = new AlertDialog.Builder(this);
        //Uncomment the below code to Set the message and title from the strings.xml file
        //builder.setMessage(R.string.dialog_message) .setTitle(R.string.dialog_title);

        //Setting message manually and performing action on button click
        builder.setMessage("If you close all your progress would not be saved... Do you wish to exit ?")
                .setCancelable(false)
                .setPositiveButton("Yes", new DialogInterface.OnClickListener() {
                    public void onClick(DialogInterface dialog, int id) {
                        finish();
                    }
                })
                .setNegativeButton("No", new DialogInterface.OnClickListener() {
                    public void onClick(DialogInterface dialog, int id) {
                        //  Action for 'NO' Button
                        dialog.cancel();
                    }
                });

        //Creating dialog box
        AlertDialog alert = builder.create();
        //Setting the title manually
        // alert.setTitle("CompQuiz");
        alert.show();
    }
}

Answer 1

You are probably passing/getting a null tableName.

Try this:

    if(b!=null){
        tableName=b.getString("table_name");
        catName=b.getString("level_name");
        Log.d("Table Name",tableName);
        Log.d("Level Name",catName);
    }

Answer 2

Try this please:

public void addQuestionsUnit1(QuestionUnit1 quest){

SQLiteDatabase db = getWritableDatabase();

db.beginTransaction();
try {
ContentValues values = new ContentValues();
values.put(KEY_QUES, quest.getQUESTION1());
values.put(KEY_ANSWER, quest.getANSWER1());
values.put(KEY_OPTA, quest.getOPTA1());
values.put(KEY_OPTB, quest.getOPTB1());
values.put(KEY_OPTC, quest.getOPTC1());
values.put(KEY_OPTD, quest.getOPTD1());
values.put(KEY_CAT,quest.getCATEGORY1());
// Inserting Row
dbase.insert(TABLE_QUEST1, null, values);
db.setTransactionSuccessful();
} catch (Exception e) {
        Log.d("DB insertion", "Error while trying to add values to database");
    } finally {
        db.endTransaction();
    }
}



@Override
public void onUpgrade(SQLiteDatabase db, int oldVersion, int newVersion) {

}

public List<QuestionUnit1> getAllQuestions1(String tname, String lname)
{
    List<QuestionUnit1> quesList1 = new ArrayList<QuestionUnit1>();
    String selectQuery1 = "SELECT * FROM " + tname+" WHERE "+KEY_CAT+" = '"+lname+"'";
    dbase= getReadableDatabase();
    Cursor cursor = dbase.rawQuery(selectQuery1, null);
    // looping through all rows and adding to list
    if (cursor.moveToFirst()) {
        do {
            QuestionUnit1 quest1 = new QuestionUnit1();
            quest1.setID1(cursor.getInt(0));
            quest1.setQUESTION1(cursor.getString(1));
            quest1.setANSWER1(cursor.getString(2));
            quest1.setOPTA1(cursor.getString(3));
            quest1.setOPTB1(cursor.getString(4));
            quest1.setOPTC1(cursor.getString(5));
            quest1.setOPTD1(cursor.getString(6));
            quesList1.add(quest1);
        } while (cursor.moveToNext());
    }
    cursor.close();
    return quesList1;
}
}