Develop Reference

Sqlite open helper insert else update?

I want to insert data successfully
Here is my code:
public void insertData(String strTableName,
ArrayList<HashMap<String, String>> arrListproductdatabase) {
db = this.getWritableDatabase();
ContentValues cv = new ContentValues();
for (int i = 0; i < arrListproductdatabase.size(); i++) {
// cv.put(columnName, arrListOfRecord.get(i).get("name"));
cv.put(columnproductname,
arrListproductdatabase.get(i).get("product"));
cv.put(columnproductprice,
arrListproductdatabase.get(i).get("price"));
cv.put(columnproductquantity,
arrListproductdatabase.get(i).get("quantity"));
cv.put(columnproductid,
arrListproductdatabase.get(i).get("productID"));
cv.put(columnresturantID,
arrListproductdatabase.get(i).get("resturantID"));
db.insert(strTableName, null, cv);
}
I want that when I have to press add button again, that time it should check if the product is already inserted, and in that condition it should update and all.
I don't want to create any duplicate value.
Any help would be appreciated!

you can check for the distinct values in the db. please follow the link to have more details
android check duplicate values before inserting data into database

Set 'Product' field as unique key. So when duplicate value arrives from standard insert, it will simply return -1 and the error message will be swallowed.
You can control the behavior by using insertWithOnConflict (String table, String nullColumnHack, ContentValues initialValues, int conflictAlgorithm) where you also specify a conflict algorithm that can be of values:
CONFLICT_ABORT
CONFLICT_FAIL
CONFLICT_IGNORE
CONFLICT_REPLACE
CONFLICT_ROLLBACK
Check out the reference for descrption of the conflict resolution types.
There is also an updateWithOnConflict

You can do that like this :
public boolean checkProduct(String product){
// shold open database here
Cursor mCursor =
db.query(true, DATABASE_TABLE, null, "product='" + product+"'", null, null, null, null, null);
if(mCursor != null){
mCursor.close();
// shold close database here
return true;
}
// shold close database first here also
return false;
}
Hope this helped you.

What is The use of moveToFirst () in SQLite Cursors

I am a programming newbie
and I found this piece of code in the internet and it works fine
Cursor c=db.query(DataBase.TB_NAME, new String[] {DataBase.KEY_ROWID,DataBase.KEY_RATE}, DataBase.KEY_ROWID+"= 1", null, null, null, null);
if(c!=null)
{
c.moveToFirst();
}
but I am not able to understand the use of the
if(c!=null)
{
c.moveToFirst();
}
part. What does it do exactly , and if I remove the
if(c!=null) { c.moveToFirst(); }
part, the code doesn't work.

The docs for SQLiteDatabase.query() say that the query methods return:
"A Cursor object, which is positioned before the first entry."
Calling moveToFirst() does two things: it allows you to test whether the query returned an empty set (by testing the return value) and it moves the cursor to the first result (when the set is not empty). Note that to guard against an empty return set, the code you posted should be testing the return value (which it is not doing).
Unlike the call to moveToFirst(), the test for if(c!=null) is useless; query() will either return a Cursor object or it will throw an exception. It will never return null.

if (c.moveToFirst()) {
while(!c.isAfterLast()) { // If you use c.moveToNext() here, you will bypass the first row, which is WRONG
...
c.moveToNext();
}
}

Cursor is not a Row of the result of query. Cursor is an object that can iterate on the result rows of your query. Cursor can moves to each row. .moveToFirst() method move it to the first row of result table.

moveToFirst() method moves the cursor to the first row. It allows to perform a test whether the query returned an empty set or not. Here is a sample of its implementation,
if (cursor.getCount() == 0 || !cursor.moveToFirst()) {
return cursor.getLong(cursor.getColumnIndexOrThrow(ID_COLUMN));
cursor.close();

what macio.Jun says is right!
we have code like below:
String sql = "select id,title,url,singer,view,info from cache where id=" + id;
SQLiteDatabase db = getMaintainer().getReadableDatabase();
Cursor query = db.rawQuery(sql, null);
query.moveToFirst();
while(query.moveToNext()){
DBMusicData entity = new DBMusicData();
entity.setId(query.getString(query.getColumnIndex(FIELD_ID)));
entity.setTitle(query.getString(query.getColumnIndex(FIELD_TITLE)));
entity.setSinger(query.getString(query.getColumnIndex(FIELD_SINGER)));
entity.setTitlepic(query.getString(query.getColumnIndex(FIELD_PICURL)));
entity.setInfoUrl(query.getString(query.getColumnIndex(FIELD_INFO)));
entity.setViews(query.getString(query.getColumnIndex(FIELD_VIEW)));
Log.w(tag, "cache:"+ entity.toString());
}
query.close();
query=null;
db.close();
db=null;
If we have only one record in the cache table, query.moveToFirst(); will cause that no record returns.

Android SQLite checking if tables contain rows

So I'm working on a game for android and I'm currently stuck at the 'load savegame' button in the main menu.
This button calls methods that read data from the database and write it into a resource class from which on this data will be accessed.
The problem is: I want to disable the load button if there are no rows in the tables, which means that no savegame exists.
To do this I used the following method:
public boolean checkForTables(){
boolean hasTables;
String[] column = new String[1];
column[0] = "Position";
Cursor cursor;
cursor = db.query("itemtable", column, null, null, null, null, null);
if(cursor.isNull(0) == true){
hasTables=false;
}else{
hasTables=true;
}
return hasTables;
As you can see it starts a query on one of the database tables and checks if the 0-column, which is the only one that should be in this cursor, is null. ATM I can't check logcat results on this call because I seem to have some problems with it, but it seems that the query throws an exception because the table is empty.
Any idea to check the tables for rows?
____________________EDIT______________
NOTE: I checked the database and it sure is empty
Okay I used a rawQuery on the table but the approach with count-statement produced an error, so I'm using
public boolean checkForTables(){
boolean hasTables;
Cursor cursor = db.rawQuery("SELECT * FROM playertable", null);
if(cursor.getCount() == 0){
hasTables=false;
if(cursor.getCount() > 0){
hasTables=true;
}
cursor.close();
return hasTables;
}
I'm using this method to decide whether or not to disable the loadGame-button which looks like this:
loadGame = (ImageButton) findViewById(R.id.loadButton);
loadGame.setEnabled(databaseAccess.checkForTables());
loadGame.setOnClickListener(new OnClickListener() {
#Override
public void onClick(View v) {
databaseAccess.loadPlayer();
databaseAccess.loadItems();
databaseAccess.dropTables();
}
});
So if checkForTables gets a rowcount of != 0 it will return true and therefore enable the Button, or disable it if rowcount = 0
Amusingly, although the tables are empty, checkForTables() returns true because getCount() seems to return a != 0 value - I just don't get it.

Perform a query such as select count(*) from itemtable. This query will yield you a single integer result, containing the number of rows in that table.
For example:
Cursor cursor = db.rawQuery("SELECT count(*) FROM itemtable");
if (cursor.getInt(0) > 0) ... // there are rows in the table
-------------------------------------------------------------------------------------
Please note that the following edit was attempted by #PareshDudhat but was rejected by reviewers. I have not kept up with Android since this answer was posted, but a very brief bit of research suggests the edit (at least the change to how rawQuery() is called, I didn't inspect the moveToFirst() but #k2col's comment suggests it is required now as well) has merit.
Cursor cursor = db.rawQuery("SELECT count(*) FROM itemtable",null);
cursor.moveToFirst();
if (cursor.getInt(0) > 0) ... // there are rows in the table

What mah says will work. Another approach you could use in your current function is:
hasTables = cursor.moveToFirst());
Note that this approach is probably only better to use if you plan on using the results of the query if hasTables is in fact true.
Also, don't forget to close your cursor when you are done with it!
EDIT
I don't know if this is your problem but in your edit you are querying for all items from the playerTable instead of the itemTable as you did in the pre-edit. Is that your problem?

cursor.getCount()
return the number of rows in database table.
and then try
Toast.makeText(this,""+cursor.getCount(),Toast.LENGTHLONG).show();
and it will give you no of rows in database table

The accepted answer put me on the right track, but didn't compile because rawQuery's method signature has changed and the cursor wasn't advanced to the first row before being read.
Here's my solution which includes error handling and closes the cursor:
public static boolean isEmpty() {
boolean isEmpty;
Cursor cursor = null;
try {
cursor = db.rawQuery("SELECT count(*) FROM itemtable", null);
if (cursor.moveToFirst()) {
isEmpty = cursor.getInt(0) == 0;
} else {
// Error handling here
}
} catch (SQLException e) {
// Error handling here
} finally {
cursor.close();
}
return isEmpty;
}

Querying a content provider that has no records?

I am working on a method that queries a content provider using a cursor. After I delete a record, it calls the loadfromProvider method and refreshes the arraylist. The content provider normally has records in it however, when I delete all the records and the query runs automatically it throws exceptions. Here is my method:
private void loadFromProvider() {
// Clear the existing array list
EQlist.clear();
ContentResolver cr = getContentResolver();
// Return all the saved records
Cursor c = cr.query(EQProvider.CONTENT_URI, null, null, null, null);
if (c.moveToFirst()) {
do {
String details = c.getString(EQProvider.DETAILS_COLUMN);
String linkString = c.getString(EQProvider.LINK_COLUMN);
EQli q = new EQli(details, linkString);
addEQToArray(q);
} while(c.moveToNext());
}
c.close();
}
When I run this with no records in the content provider it throws the following:
java.lang.IndexOutOfBoundsException: Invalid index 1, size is 1
at java.util.ArrayList.throwIndexOutOfBoundsException(ArrayList.java:257)
I think this is due to the cursor trying to parse a null value. I am trying to figure out a way that if the cursor does not come back with any records, it bypasses the rest of the code and does nothing happens.
Any help would be appreciated. Thanks

If there are no records your cursor should be empty. If the cursor is empty then c.moveToFirst() will return false and you are not going to enter the do-while loop.
Debug your application and make sure that the cursor is empty.

Android SQLiteDatabase: Reading one column

I have a one row database just for saving app data. My goal is to read one column (one value) from it.
This query returns all the columns in a Cursor:
public Cursor readAll() {
return getReadableDatabase().query(tableName, null, null, null, null, null, null);
}
It returns a Cursor with one row in it, just perfect. However, I don't want to read all columns at once, because it's slow as I have blob's in db too.
Instead, I'd like to read just one column at a time, separately. For example, for a column called "TEXT" it would be this:
public Cursor readText() {
String[] projection = new String[]{"TEXT"};
return getReadableDatabase().query(tableName, projection, null, null, null, null, null);
}
However, this won't work, as I get back a Cursor with zero rows.
So, how to read a specific column from SQLiteBatabase in Android?

public Cursor readText() {
return getReadableDatabase().rawQuery("SELECT colName FROM myTable", new String[] {});
}

Syntax seems to be correct. Check please that you use right name of the column. Showing the table generation code and actual query code could help.

You can use this one also
public Cursor readText() {
return getReadableDatabase().rawQuery("SELECT column_name FROM table_name", null);
}