Develop Reference

Why sqlite distinct doesn't work

I am using Loader to get data from db and I have some trouble whit distinct, in simple words - distinct doesn't work. here is my code:
private String[] CONTACTS_COLUMNS ={
"DISTINCT " + ContactsEntry.CONTACT_ID + " AS _id",
ContactsEntry.CONTACT_FROM,
ContactsEntry.CONTACT_NAME,
CardsPhonesEntry.CONTACT_PHONE,
CardsPhonesEntry.CARD_NUMBER
};
#Override
public Loader<Cursor> onCreateLoader(int id, Bundle args) {
return new CursorLoader(getActivity(),
ContactsEntry.CONTENT_URI,
CONTACTS_COLUMNS,
mSelection, null, null);
}
here is some code from my contentProvider:
#Nullable
#Override
public Cursor query(Uri uri, String[] projection, String selection, String[] selectionArgs, String sortOrder) {
Cursor retCursor;
int match = sUriMatcher.match(uri);
switch (match){
case PEOPLE:
retCursor = getAllContacts(projection, selection, selectionArgs, sortOrder);
break;
default:
throw new UnsupportedOperationException("Unknown uri in query(): " + uri);
}
return retCursor;
}
private Cursor getAllContacts(String[] projection, String selection, String[] selectionArgs,
String sortOrder){
return sPeopleWithCardsAndPhones.query(
mDbHelper.getReadableDatabase(),
projection,
selection,
selectionArgs,
null, null,
sortOrder
);
}
static {
sPeopleWithCardsAndPhones = new SQLiteQueryBuilder();
sPeopleWithCardsAndPhones.setTables(
ContactsEntry.TABLE_NAME + " LEFT JOIN " + CardsPhonesEntry.TABLE_NAME + " ON " +
ContactsEntry.TABLE_NAME + "." + ContactsEntry.CONTACT_ID + " = " +
CardsPhonesEntry.TABLE_NAME + "." + CardsPhonesEntry.OWNER_ID
);
}
what i am doing wrong and why distinct doesn't want to work?
EDIT:
For example: I have 1 contact in first table, and in the second table there are 2 cards linked to this contact by contact_id;
I need to show list with only 1 item (first contact) without depending how much cards it has. and now when init loader - it shows me this contact twice, but not once.

Android Content provider Cursor returns 0

I have looked at this for a couple of days now and I completely can't work out why my content provider return 0 using the arguments I am passing it.
Here's my contentResolver code:
String[] expenditureProjection = {
BusinessOpsDatabase.COL_EXPEND_CAT_ID,
BusinessOpsDatabase.COL_EXPEND_DATE,
BusinessOpsDatabase.COL_EXPEND_AMOUNT,
BusinessOpsDatabase.COL_EXPEND_DESC,
BusinessOpsDatabase.COL_STERLING_EXCHANGE,
BusinessOpsDatabase.COL_COMPANY_ID,
BusinessOpsDatabase.CURRENCY_ID,
BusinessOpsDatabase.COL_MOD_DATE
};
// Defines a string to contain the selection clause
String selectionClause = null;
// An array to contain selection arguments
String[] selectionArgs = {expend_id.trim()};
selectionClause = BusinessOpsExpenditureProvider.EXPENDITURE_ID + "=?";
Log.d(TAG, expend_id+" Selected from list.");
Cursor expendCursor = getContentResolver().query(
BusinessOpsExpenditureProvider.CONTENT_URI, expenditureProjection, selectionClause, selectionArgs, null);
if (null == expendCursor) {
Log.d(TAG, "Expenditure cursor: Is null");
} else if (expendCursor.getCount() < 1) {
Log.d(TAG,"Expenditure cursor: Search was unsuccessful: "+expendCursor.getCount());
} else {
Log.d(TAG,"Expenditure cursor: Contains results");
int i=0;
expendCursor.moveToFirst();
// loop through cursor and populate country array
while (expendCursor.isAfterLast() == false)
{
expend_date_edit.setText(expendCursor.getString(1));
expend_amount_edit.setText(expendCursor.getString(3));
expend_desc_edit.setText(expendCursor.getString(4));
i++;
expendCursor.moveToNext();
}
}
Here's my content provider query method:
#Override
public Cursor query(Uri uri, String[] projection, String selection,
String[] selectionArgs, String sortOrder) {
SQLiteDatabase db = mDB.getWritableDatabase();
// A convenience class to help build the query
SQLiteQueryBuilder qb = new SQLiteQueryBuilder();
qb.setTables(BusinessOpsDatabase.TABLE_EXPENDITURE);
switch (sURIMatcher.match(uri)) {
case EXPENDITURE:
if(selection != null && selectionArgs != null){
//values.get("company_contact");
String segment = uri.getLastPathSegment();
Log.d(TAG, "Last path segment: "+ segment);
String whereClause = BusinessOpsDatabase.EXPENDITURE_ID + "="+ selectionArgs[0];
Log.d(TAG, "Where clause: "+whereClause);
}
break;
case EXPENDITURE_ID:
// If this is a request for an individual status, limit the result set to that ID
qb.appendWhere(BusinessOpsDatabase.EXPENDITURE_ID + "=" + uri.getLastPathSegment());
break;
default:
throw new IllegalArgumentException("Unsupported URI: " + uri);
}
// Query the underlying database
Cursor c = qb.query(db, projection, selection, selectionArgs, null, null, null);
// Notify the context's ContentResolver if the cursor result set changes
c.setNotificationUri(getContext().getContentResolver(), uri);
// Return the cursor to the result set
return c;
}
I'm printing the whereclause to the log and I see '_id=3' which should be fine because I have pulled off a copy of my SQLite database and I can see that the expenditure table has an _id 3 row in it. Any Ideas?

What an epic problem this has been. I found the error in my ContentResolver code.
selectionClause = BusinessOpsExpenditureProvider.EXPENDITURE_ID + "=?";
I was using the EXPENDITURE_ID variable from the provider rather than the database class. The line now reads.
selectionClause = BusinessOpsDatabase.EXPENDITURE_ID + "=?";
And works!

Selecting NULL values in Android SQLite

I'm executing the following method with no success beacause of the selectArgs being incorrect (at least this is what I believe.
findAll:
public Collection<Object> findAllByCodigoSetorOrderByStatusWhereDataAgendamentoIsNull(Integer vendedor) {
Collection<Object> objects = null;
String selection = Object.FIELDS[20] + "=?" + " OR " + Object.FIELDS[20] + "=?" + " OR " + Object.FIELDS[20] + "=?" + " AND " + Object.FIELDS[6] + "=?";
String[] selectionArgs = new String[] { "''", "'null'", "NULL", String.valueOf(vendedor) };
Collection<ContentValues> results = findAllObjects(Object.TABLE_NAME, selection, selectionArgs, Object.FIELDS, null, null, Object.FIELDS[4]);
objects = new ArrayList<Object>();
for (ContentValues result : results) {
objects.add(new Object(result));
}
return objects;
}
findAllObjects:
protected Collection<ContentValues> findAllObjects(String table, String selection, String[] selectionArgs, String[] columns, String groupBy, String having, String orderBy) {
Cursor cursor = null;
ContentValues contentValue = null;
Collection<ContentValues> contentValues = null;
try {
db = openRead(this.helper);
if (db != null) {
cursor = db.query(table, columns, selection, selectionArgs, groupBy, having, orderBy);
contentValues = new ArrayList<ContentValues>();
for (int i = 0; i < cursor.getCount(); i++) {
cursor.moveToPosition(i);
contentValue = new ContentValues();
for (int c = 0; c < cursor.getColumnCount(); c++) {
contentValue.put(cursor.getColumnName(c), cursor.getString(c));
}
contentValues.add(contentValue);
cursor.moveToNext();
}
}
return contentValues;
} finally {
close(db);
}
}
How can I correctly select and compare a column to - null, 'null' and '' using the db.query?

Android's database API does not allow to pass NULL values as parameters; it allows only strings.
(This is a horrible design bug. Even worse, SQLiteStatement does allow all types for parameters, but works only for queries that return a single value.)
You have no choice but to change the query string to blah IS NULL.

Old question but i was still stuck on this for a few hours until i found this answer. For whatever reason this strange behaviour (or bug) still exists within the android sdk, if you want to query against null values simply do
SQLiteDatabase db = getReadableDatabase();
ContentValues contentValues = new ContentValues();
contentValues.put("columnName", newValue);
String nullSelection = "columnName" + " IS NULL";
db.update("tableName", contentValues, nullSelection, null);
db.close();
In this example i am updating values, but it is a similar concept when just selecting values

As mentioned in other answers, for null "IS NULL" need to be used. Here is some convenience code for having both null and strings (I'm using delete in the example but the same can be done for other methods, e.g. query):
public void deleteSomething(String param1, String param2, String param3) {
ArrayList<String> queryParams = new ArrayList<>();
mDb.delete(TABLE_NAME,
COLUMN_A + getNullSafeComparison(param1, queryParams) + "AND " +
COLUMN_B + getNullSafeComparison(param2, queryParams) + "AND " +
COLUMN_C + getNullSafeComparison(param3, queryParams),
queryParams.toArray(new String[0]));
}
private String getNullSafeComparison(String param, List<String> queryParams) {
if (param == null) {
return " IS NULL ";
} else {
queryParams.add(param);
return " = ? ";
}
}

You can bind NULL values to SQLiteStatement:
SQLiteDatabase db = getWritableDatabase();
SQLiteStatement stmt = db.compileStatement("UPDATE table SET " +
"parameter=? WHERE id=?");
if (param == null)
stmt.bindNull(1);
else
stmt.bindString(1, param);
stmt.execute();
stmt.close();
db.close();

How do I order my SQLITE database in descending order, for an android app?

What is the most efficient method of showing my data in descending order?
public String getRank() {
String[] rank = new String[]{ KEY_ROWID };
Cursor c = scoreDb.query(DATABASE_TABLE, rank, null, null, null, null, null); //reading information from db.
String rankResult = "";
int iRow = c.getColumnIndex(KEY_ROWID); //Cursor looking for column setting equal to these ints.
for (c.moveToFirst(); !c.isAfterLast(); c.moveToNext()) {
//Move to first row - where cursor starts and moves to next row as long it is not after last row.
rankResult = rankResult + c.getString(iRow) + "\n";
//Returning value of row that it is currently on.
}
return rankResult; //returning result
}
public String getName() {
String[] name = new String[]{ KEY_NAME };
Cursor c = scoreDb.query(DATABASE_TABLE, name, null, null, null, null, null); //reading information from db.
String nameResult = "";
int iRow1 = c.getColumnIndex(KEY_NAME); //Cursor looking for column setting equal to these ints.
for (c.moveToFirst(); !c.isAfterLast(); c.moveToNext()) {
//Move to first row - where cursor starts and moves to next row as long it is not after last row.
nameResult = nameResult + c.getString(iRow1) + "\n";
//Returning value of row that it is currently on.
}
return nameResult; //returning result
}
public String getScore() {
String[] score = new String[]{ KEY_SCORE };
Cursor c = scoreDb.query(DATABASE_TABLE, score, null, null, null,null, null); //reading information from db.
String scoreResult = "";
int iRow2 = c.getColumnIndex(KEY_SCORE); //Cursor looking for column setting equal to these ints.
for (c.moveToFirst(); !c.isAfterLast(); c.moveToNext()) {
//Move to first row - where cursor starts and moves to next row as long it is not after last row.
scoreResult = scoreResult + c.getString(iRow2) + "\n";
//Returning value of row that it is currently on.
}
return scoreResult; //returning result
}

Query has two syntax, the syntax you are using, last column represents orderBy, you just need to specify on what column you want to do orderBy +"ASC" (or) orderBy +"DESC"
Cursor c = scoreDb.query(DATABASE_TABLE, rank, null, null, null, null, yourColumn+" DESC");
Refer this documentation to understand more about query() method.

return database.rawQuery("SELECT * FROM " + DbHandler.TABLE_ORDER_DETAIL +
" ORDER BY "+DbHandler.KEY_ORDER_CREATED_AT + " DESC"
, new String[] {});

Cursor c = scoreDb.query(Table_Name, score, null, null, null, null, Column+" DESC");
Try this

According to docs:
public Cursor query (String table, String[] columns, String selection, String[] selectionArgs, String groupBy, String having, String orderBy, String limit);
and your ORDER BY param means:
How to order the rows, formatted as an SQL ORDER BY clause
(excluding the ORDER BY itself). Passing null will use the default
sort order, which may be unordered.
So, your query will be:
Cursor cursor = db.query(TABLE_NAME, null, null,
null, null, null, KEY_ITEM + " DESC", null);

public List getExpensesList(){
SQLiteDatabase db = this.getWritableDatabase();
List<String> expenses_list = new ArrayList<String>();
String selectQuery = "SELECT * FROM " + TABLE_NAME ;
Cursor cursor = db.rawQuery(selectQuery, null);
try{
if (cursor.moveToLast()) {
do{
String info = cursor.getString(cursor.getColumnIndex(KEY_DESCRIPTION));
expenses_list.add(info);
}while (cursor.moveToPrevious());
}
}finally{
cursor.close();
}
return expenses_list;
}
This is my way of reading the record from database for list view in descending order. Move the cursor to last and move to previous record after each record is fetched. Hope this helps~

Cursor c = myDB.rawQuery("SELECT distinct p_name,p_price FROM products order by Id desc",new String[]{});
this works for me!!!

you can do it with this
Cursor cursor = database.query(
TABLE_NAME,
YOUR_COLUMNS, null, null, null, null, COLUMN_INTEREST+" DESC");

SQLite ORDER BY clause is used to sort the data in an ascending or descending order, based on one or more columns.
Cursor c = scoreDb.query(DATABASE_TABLE, rank, null, null, null, null, yourColumn+" DESC");
SQLiteDatabase db = this.getReadableDatabase();
Cursor cursor = db.query(
TABLE_NAME,
rank,
null,
null,
null,
null,
COLUMN + " DESC",
null);

We have one more option to do order by
public Cursor getlistbyrank(String rank) {
try {
//This can be used
return db.`query("tablename", null, null, null, null, null, rank +"DESC",null );
OR
return db.rawQuery("SELECT * FROM table order by rank", null);
} catch (SQLException sqle) {
Log.e("Exception on query:-", "" + sqle.getMessage());
return null;
}
}
You can use this two method for order

This a terrible thing! It costs my a few hours!
this is my table rows :
private String USER_ID = "user_id";
private String REMEMBER_UN = "remember_un";
private String REMEMBER_PWD = "remember_pwd";
private String HEAD_URL = "head_url";
private String USER_NAME = "user_name";
private String USER_PPU = "user_ppu";
private String CURRENT_TIME = "current_time";
Cursor c = db.rawQuery("SELECT * FROM " + TABLE +" ORDER BY " + CURRENT_TIME + " DESC",null);
Every time when I update the table , I will update the CURRENT_TIME for sort.
But I found that it is not work.The result is not sorted what I want.
Finally, I found that, the column "current_time" is the default row of sqlite.
The solution is, rename the column "cur_time" instead of "current_time".

About efficient method. You can use CursorLoader. For example I included my action. And you must implement ContentProvider for your data base. https://developer.android.com/reference/android/content/ContentProvider.html
If you implement this, you will call you data base very efficient.
public class LoadEntitiesActionImp implements LoaderManager.LoaderCallbacks<Cursor> {
public interface OnLoadEntities {
void onSuccessLoadEntities(List<Entities> entitiesList);
}
private OnLoadEntities onLoadEntities;
private final Context context;
private final LoaderManager loaderManager;
public LoadEntitiesActionImp(Context context, LoaderManager loaderManager) {
this.context = context;
this.loaderManager = loaderManager;
}
public void setCallback(OnLoadEntities onLoadEntities) {
this.onLoadEntities = onLoadEntities;
}
public void loadEntities() {
loaderManager.initLoader(LOADER_ID, null, this);
}
#Override
public Loader<Cursor> onCreateLoader(int id, Bundle args) {
return new CursorLoader(context, YOUR_URI, null, YOUR_SELECTION, YOUR_ARGUMENTS_FOR_SELECTION, YOUR_SORT_ORDER);
}
#Override
public void onLoadFinished(Loader<Cursor> loader, Cursor cursor) {
}
#Override
public void onLoaderReset(Loader<Cursor> loader) {
}

Union of Tables with Cursor in Android

I am trying to UNION two tables with the same fields to create a single cursor (through a content provider) that I am using to create my ListView.
#Override
public Cursor query(Uri uri, String[] projection, String selection,
String[] selectionArgs, String sortOrder) {
SQLiteQueryBuilder qb = new SQLiteQueryBuilder();
String groupBy = null;
switch (sUriMatcher.match(uri)) {
case LIST:
StringBuilder sb = new StringBuilder();
for (String s : projection)
sb.append(s).append(",");
String projectionStr = sb.toString();
projectionStr = projectionStr.substring(0,
projectionStr.length() - 1);
String[] subQueries = new String[] {
"SELECT " + projectionStr + " FROM " + Customer.TABLE_NAME,
"SELECT " + projectionStr + " FROM "
+ IndividualCustomer.TABLE_NAME };
String sql = qb.buildUnionQuery(subQueries, sortOrder, null);
SQLiteDatabase db = mDatabaseHelper.getReadableDatabase();
Cursor mCursor = db.rawQuery(sql, null);
mCursor.setNotificationUri(getContext().getContentResolver(), uri);
return mCursor;
Even if the two tables are empty, I get two null rows, which creates two rows in my listview. How do I get rid of this problem?
Additionally, when I delete a row from the ListView, the cursor is not getting updated in spite of setNotificationUri()
Any pointers, will be most appreciated

Solved - I had to supply a group by clause as one of the columns (of the projection) had a "TOTAL(...)" function.