Why does a delete rawQuery need a moveToFirst in order to actually delete the rows?

Question

I have been struggling for hours trying to debug why the following delete query actually didn\'t delete anything even if the exact same query on the exact same database work

Answer 1

The answer why is because rawQuery actually doesn't execute til u call some method on returned cursor. moveToFirst, isAfterLast ..

Answer 2

I cannot answer the why, but another solution is to use .execSQL(String) as posted here

Answer 3

In my case also, the same thing has happened for DELETE, It ran successfully after calling "cursor.moveToFirst()". Same is the case with INSERT and UPDATE queries also. I have also observed that calling any method on the cursor for the above mentioned queries I have got the results correctly. Without calling any method of the cursor the desired effect is taking place. So, I think the answer to your question is : Query gets executed only when we call some method on the cursor.

Answer 4

A rawQuery returns a Cursor of a result set, which is just a reference to the query results. You should just be using a straight delete() call. Take a look at the documentation:

http://developer.android.com/reference/android/database/sqlite/SQLiteDatabase.html

or an SQLiteStatement:

http://developer.android.com/reference/android/database/sqlite/SQLiteStatement.html

Answer 5

Following example shows how it return cursor by rawQuery if we do not need to write moveToFirst().

public Cursor deleteContact(int id) {
    SQLiteDatabase db = this.getWritableDatabase();
    db.delete(TABLE_CONTACTS, KEY_ID + " = ?",new String[]{String.valueOf(id)});
    Cursor c = db.rawQuery("DELETE FROM "+TABLE_CONTACTS+" WHERE "+KEY_ID+" = "+id,null);
    db.close();

    //if we not return Type Cursor then in above code:
    // db.rawQuery("DELETE FROM "+TABLE_NAME+" WHERE "+KEY_ID+" = "+id,null).moveToFirst();
    // in this way no return Type necessary.
    return c;
}