SQLIte query returns empty cursor

Question

I am trying to get data from my SQLite database in Android using this query.

Cursor cursor = db.rawQuery("SELECT * FROM Task where taskId = 1 ", null);

However the cursor is returned empty, a taskId with value 1 exists.

If I do this

Cursor cursor = db.rawQuery("SELECT * FROM Task", null);

my cursor contains all of the values - including a taskId with value 1.

I have tried all of the following commands as well, neither of them worked:

Cursor cursor = db.rawQuery("SELECT * FROM Task where taskId = " + 1, null);
Cursor cursor = db.rawQuery("SELECT * FROM Task where taskId = " + "'1'", null);
Cursor cursor = db.rawQuery("SELECT * FROM Task where taskId = ?", new String[]{"1"});

taskId is of type Integer, tried it with Text, too, also didn't work.

Is there something I didn't consider? Help would be highly appreciated!

EDIT: Code for creating the database:

CREATE TABLE Task + " (" +
        _id INTEGER PRIMARY KEY," +
        "taskDescription TEXT, +                
        "taskId INTEGER," +
        "taskName TEXT" + 
        "PreviousTaskID " + "REFERENCES " + "PreviousTasks " + 
        "(" + PreviousTasks._ID + "))"

Pff, still nothing wrong... are you sure you're not mixing the _id field with taskId?? — Merlevede
– Merlevede, Commented Feb 23, 2014 at 18:48

Andreas Grapentin · Accepted Answer · 2016-09-13 04:57:54Z

9

Cursor cursor = null;
String Query ="SELECT * FROM Task where taskId = 1 ";
cursor = sqldb.rawQuery(Query, null);

if (cursor != null && cursor.moveToFirst()) {
  do {
    // ...
  } while (cursor.moveToNext());

  cursor.close();
}

i hope its useful to you..

edited Sep 13, 2016 at 4:57

Andreas Grapentin

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answered Feb 24, 2014 at 8:38

dipali

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Comments

Smile2Life · Accepted Answer · 2014-02-23 19:38:20Z

1

If you created database for example with 4 fields and used this db then if you add new field you need to recreate database on phone, delete and create it.

Your database must be at /data/data/com.yourapp.package/databases/, use this or this open it and check if anything wrong.

Remove all spaces :

Cursor cursor = getReadableDatabase().rawQuery("SELECT  * FROM  Task WHERE taskId=1", null);

Step the cursor to the first result :

cursor.moveToFirst();

Use getInt:

int taskid = c.getnt(c.getColumnIndex("taskId"));

edited Feb 23, 2014 at 19:38

answered Feb 23, 2014 at 19:11

Smile2Life

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Comments

deimos1988 · Accepted Answer · 2014-02-23 22:08:41Z

1

I just found out what the problem was: When accessing the cursor, I used following code:

cursor.moveToFirst();
while(cursor.moveToNext()){
  //stuff
};

Instead what I had to do was this:

cursor.moveToFirst();
do{
  //stuff
} while(cursor.moveToNext());

I didn't notice the error when I queried

Cursor.rawQuery("SELECT * FROM TASK");

since my cursor had more than one entry and. But when I queried

Cursor.rawQuery("SELECT * FROM TASK WHERE taskID=1");

the cursor only has one entry which was skipped because of the while-loop.

answered Feb 23, 2014 at 22:08

deimos1988

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1 Comment

laalto Over a year ago

FYI, this will fail in case there is no data. You should check the return value of moveToFirst(), too.

user3522383 · Accepted Answer · 2016-02-10 19:07:09Z

0

If you mean -1 count of elements of cusor by telling "empty", so you just have to use moveToFirst() before.

Cusror c = rawQuery(...); 
// this line is required 
c.moveToFirst();

then if you'd try to invoke

c.getCount()

it returns != 0 (if the query returns more than 0).

answered Feb 10, 2016 at 19:07

user3522383

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