Develop Reference

Dynamic SQLite queries

I'm trying to implement dynamic queries in my Android app, to let the users search according to some criteria. In this case I'm trying to search simply by an integer value. Here's my attempt:
...
public String[][] listarNegocio(int idProyecto,
int minimo,
int maximo)
{
String[][] arrayDatos = null;
String[] parametros = {String.valueOf(idProyecto)};
Cursor cursor = null;
cursor = querySQL("SELECT *" +
" FROM negocio" +
" WHERE ? in (0, id_proyecto)", parametros);
if(cursor.getCount() > 0)
{
int i = minimo - 1;
arrayDatos = new String[maximo - minimo + 1][20];
while(cursor.moveToNext() && i < maximo)
{
// Here I fill the array with data
i = i + 1;
}
}
cursor.close();
CloseDB();
return(arrayDatos);
}
public Cursor querySQL(String sql, String[] selectionArgs)
{
Cursor oRet = null;
// Opens the database object in "write" mode.
db = oDB.getReadableDatabase();
oRet = db.rawQuery(sql, selectionArgs);
return(oRet);
}
...
I tested this query using SQLFiddle, and it should return only the rows where the column id_proyecto equals the parameter idProyecto, or every row if idProyecto equals 0. But it doesn't return anything. If I remove the WHERE clause and replace "parametros" with "null", it works fine.
Additionally, I need to search by text values, using LIKE. For example, WHERE col_name LIKE strName + '%' OR strName = ''. How should I format my parameters and the query to make it work?

You should do one query for each case. For an id that exists, do SELECT * FROM negocio WHERE id_proyecto = ?. For an id that doesn't exist (I'm assuming 0 isn't a real id), just query everything with SELECT * FROM negocio.
Code should be something like this:
if(parametros[0] != 0){
cursor = querySQL("SELECT *" +
" FROM negocio" +
" WHERE id_proyecto = ?", parametros);
} else {
cursor = querySQL("SELECT *" +
" FROM negocio", null);
}
Regarding your second question, it depends on what you're looking for, you could use LIKE '%param%' or CONTAINS for occurrences in between text, LIKE param for partial matches or just = param if you're looking an exact match.

Android - How can I pass data related to two tables to a the insert method of a Content Provider

I need to insert data related to an Order and its corresponding Detail.
Without a ContentProvider I would do something like this:
public boolean insertOrder(Order order, ArrayList<OrderDetail> items) {
boolean wasSuccessful = false;
ContentValues cvOrder = new ContentValues();
cvPedido.put(ORDER_CUSTOMER_ID, order.getCustomerId());
cvPedido.put(ORDER_CUSTOMER_NAME, order.getCustomerName());
String insertQuery = "INSERT INTO " + ORDER_DETAIL_TABLE
+ " VALUES (?,?)";
//...
try {
this.openWriteableDB();
SQLiteStatement statement = db.compileStatement(insertQuery);
db.beginTransaction();
long idOrder = db.insertOrThrow(ORDER_TABLE, null, cvOrder);
if (idOrder > 0) {
for (int i = 0; i < items.size(); i++) {
OrderDetail detail=items.get(i);
statement.clearBindings();
statement.bindString(1, detail.getDescription);
statement.bindDouble(2, detail.getPrice);
//...
statement.execute();
}
db.setTransactionSuccessful();
wasSuccessful = true;
}
} finally {
db.endTransaction();
this.closeDB();
}
return wasSuccessful;
}
The problem is that now I want to use a ContentProvider and I don't know what to do with this kind of cases where data about two or more tables must be passed to a single CRUD operation, knowing that a insert operation only accepts two parameters :
#Override
public Uri insert(Uri uri, ContentValues values) {
}
What do you do in a ContentProvider when you have to insert relational data in a transaction?
Thanks in advance.

You should use ContentProviderOperation. Since it's your ContentProvider you can assure that applyBatch() will execute all operations within a transaction. All standard content providers also ensure that that's the case.
See my blog post about ContentProviderOperation in general and my other post about how to use withBackReference() to access results of previous operations - which you need to access the orderId.
One important caveat: All ContentProviderOperations of one batch must use the same authority - but can use different URIs! In your case that should be no problem.

You can put all the data into a ContentValues and have a provider. You'll have to get a little creative with the order details.
Below psuedo code I create a key "DETAIL" on the fly with a integer then the item.
ContentValues values = new ContentValues();
values.put(ORDER_ID,orderid);
for (int i = 0; i < items.size(); i++) {
values.put("DETAIL" + Integer.ToString(i),items.get(i));
}
Uri uri = context.getContentResolver().insert(
ORDER_URI, values);
Then in content provider you sort it out.
#Override
public Uri insert(Uri uri, ContentValues values) {
int uriType = sURIMatcher.match(uri);
SQLiteDatabase sqlDB = database.getWritableDatabase();
long id = 0;
switch (uriType) {
case ORDER:
// trim name and description
trimNameDescriptions(values);
try {
id = sqlDB.insertOrThrow(ORDERS_TABLE,
null, values);
Integer i =0;
do (values.containsKey("DETAIL" + i.toString()){
ContentValues v = new ContentValues();
v.put("DETAIL",values.get("Detail" + i.toString()));
v.put("ORDERID",id);
//ACTUALLY CALL THE INSERT METHOD OF THE PROVIDER
insert(DETAIL_URI,v);
i+=1;
}

You can design content provider to mirror your SQLite tables, and use insertOrder code same as above.
Just use insert of content providers for each table(uri), to perform similar operations as in your insertOrder method
Another option is to define your content provider URI to take combination of your Order and items , and implement the parsing yourself in the content provider before committing to underlying data model.

Check if some string is in SQLite database

I have some trouble with a SQLite database with 1 table and 2 columns, column_id and word. I extended SQLiteAssetHelper as MyDatabase and made a constructor:
public MyDatabase(Context context) {
super(context, DATABASE_NAME, null, DATABASE_VERSION);
}
I need to check whether some string is in the database (in column word). I tried to modify the code from answer provided by Benjamin and dipali, but I used SQLiteAssetHelper and I can't get it to work. The method that I have in mind receives the string to search for as a parameter and returns a boolean if string is in the database.
public boolean someMethod(String s)
In addition, I tried to put the check on a background thread with AsyncTask because I have 60 strings to check.

TABLE_NAME and COLUMN_WORD should be self-explanatory.
public boolean someMethod(String s) {
SQLiteDatabase db = getReadableDatabase();
String[] columns = new String[] {COLUMN_WORD};
String where = COLUMN_WORD + " = ?";
String[] whereArgs = new String[] {s};
// select column_word from table where column_word = 's' limit 1;
Cursor cursor = db.query(TABLE_NAME, columns, where, whereArgs, null, null, null, "1");
if (cursor.moveToFirst()) {
return true; // a row was found
}
return false; // no row was found
}
You can do this in the background, but I don't think for a query like this it's even necessary.
EDIT
There are some improvements that should be made to the above for the sake of correctness. For one thing, the Cursor should be closed since it is no longer being used. A try-finally block will ensure this:
Cursor cursor = db.query(...);
try {
return cursor.moveToFirst();
} finally {
cursor.close();
}
However, this method doesn't need to obtain a whole `Cursor. You can write it as follows and it should be more performant:
public boolean someMethod(String s) {
SQLiteDatabase db = getReadableDatabase();
String sql = "select count(*) from " + TABLE_NAME + " where "
+ COLUMN_WORD + " = " + DatabaseUtils.sqlEscapeString(s);
SQLiteStatement statement = db.compileStatement(sql);
try {
return statement.simpleQueryForLong() > 0;
} finally {
statement.close();
}
}
You could add a catch block and return false if you think it's possible (and valid) to encounter certain exceptions like SQLiteDoneException. Also note the use of DatabaseUtils.sqlEscapeString() because s is now concatenated directly into the query string and thus we should be wary of SQL injection. (If you can guarantee that s is not malicious by the time it gets passed in as the method argument, then you could theoretically skip this, but I wouldn't.)

because of possible data leaks best solution via cursor:
Cursor cursor = null;
try {
cursor = .... some query (raw or not your choice)
return cursor.moveToNext();
} finally {
if (cursor != null) {
cursor.close();
}
}
1) From API KITKAT u can use resources try()
try (cursor = ...some query)
2) if u query against VARCHAR TYPE use '...' eg. COLUMN_NAME='string_to_search'
3) dont use moveToFirst() is used when you need to start iterating from beggining
4) avoid getCount() is expensive - it iterates over many records to count them. It doesn't return a stored variable. There may be some caching on a second call, but the first call doesn't know the answer until it is counted.

Bulk inserting using an array of ContentValues

im trying to do a batch insert of about 700 floats. The method i'm using is below and as well as the content provider's bulkInsert. The issue is that when i put all the floating point values into the ContentValues nothing happens. What's a better way to insert those floating point values into the ContentValues object?
private void saveToDatabase( float[] tempValues )
{
ContentValues values = new ContentValues();
// WM: TODO: add patient id and sensor type
for (float tempVal : tempValues){
values.put( DataTable.COLUMN_DATA, tempVal );
}
ContentValues[] cvArray = new ContentValues[1];
cvArray[0] = values;
ContentResolver resolver = getContentResolver();
resolver.bulkInsert( HealthDevContentProvider.CONTENT_URI_DATA, cvArray);
public int bulkInsert(Uri uri, ContentValues[] values){
int numInserted = 0;
String table = null;
int uriType = sURIMatcher.match(uri);
switch (uriType) {
case RAWINPUT_TABLE:
table = RAWINPUT_TABLE_PATH;
break;
}
db.beginTransaction();
try {
for (ContentValues cv : values) {
long newID = db.insertOrThrow(table, null, cv);
if (newID <= 0) {
throw new SQLException("Failed to insert row into " + uri);
}
}
db.setTransactionSuccessful();
getContext().getContentResolver().notifyChange(uri, null);
numInserted = values.length;
} finally {
db.endTransaction();
}
return numInserted;
}

If you want each float to have it's own record in your database, you need an instance of ContentValues for each new record. Right now you have one instance of ContentValues and you are writing the same key to it (meaning you are writing over the value) 700 times.
private void saveToDatabase( float[] tempValues ) {
final int count = tempValues.legnth;
ContentValues[] cvArray = new ContentValues[count];
for (int i = 0; i < count; i++) {
float tempVal = tempValues[i];
ContentValues values = new ContentValues();
values.put( DataTable.COLUMN_DATA, tempVal );
cvArray[i] = values;
}
/* all the rest */
}

I know that this will be rude, but just throw away this code. Providers have primary methods to deal with most SQLite operations and you tried to blend three of them (insert(), bulkInsert(), and applyBatch()) into some kind of Frankenstein. Here are the main mistakes:
1) This line values.put(DataTable.COLUMN_DATA, tempVal) is not inserting new entries at each iteration; it is overriding them. After all iterations, values contains only the 700th float value of your array.
2) As #Karakuri remembered, there is only one ContentValues instance inside cvArray. bulkInsert() doc states about its second parameter:
An array of sets of column_name/value pairs to add to the database. This must not be null.
So cvArray must contain a ContentValues instance (a set) for every entry you want to insert into the database.
3) Not exactly an error, but something you should watch out. There are no guarantees that mTables will exist, and trying to make operations without specifying a table will throw a SQLException.
4) These three lines are basically useless:
if (newId <= 0) {
throw new SQLException("Failed to insert row into " + uri);
}
insertOrThrow() already throws an exception if some error happens during the insert operation. If you want to check manually for an error, try insert() or insertWithOnConflict() (or add a catch to your try block and deal with the exception there).
5) And finally, there is the problem about numInserted #petey pointed (and there's no need to repeat).
One last advice: forget that bulkInsert() exists. I know that this will require more lines of code, but using applyBatch() you can achieve better results (and more easily, since you do not have to implement it). Wolfram Rittmeyer wrote a series of excellent articles about transactions, check if you have any doubt.
Last but not least (yes, I'm in a good mood today), this is how I would do a basic implementation of your code:
#Override
public Uri insert(Uri uri, ContentValues values) {
final SQLiteDatabase db // TODO: retrieve writable database
final int match = matcher.match(uri);
switch(match) {
case RAWINPUT_TABLE:
long id = db.insert(RAWINPUT_TABLE, null, values); // TODO: add catch block to deal.
getContext().getContentResolver().notifyChange(uri, null, false);
return ContentUris.withAppendedId(uri, id);
default:
throw new UnsupportedOperationException("Unknown uri: " + uri);
}
}
private void saveToDatabase( float[] tempValues ) {
ArrayList<ContentProviderOperation> operations = new ArrayList<ContentProviderOperation>();
for (float tempVal : tempValues){
operations.add(ContentProviderOperation
.newInsert(HealthDevContentProvider.CONTENT_URI_DATA)
.withValue(DataTable.COLUMN_DATA, tempVal).build();
.withValue() // TODO: add patient id
.withValue() // TODO: add sensor type);
}
// WARNING!! Provider operations (except query if you are using loaders) happen by default in the main thread!!
getContentResolver().applyBatch(operations);
}

I use batch inserts, not sure what the difference between bulk and batch is but all I do is this
ArrayList<ContentProviderOperation> operations = new ArrayList<ContentProviderOperation>();
for(int j=0;j<locationAry.length;j++){
ContentValues values2 = new ContentValues();
values2.put(MapPoints.ELEMENT_ECM2ID, ecm2id);
values2.put(MapPoints.ELEMENT_ID, newElementId);
values2.put(MapPoints.LATITUDE, locationAry[j+1]);
values2.put(MapPoints.LONGITUDE, locationAry[j]);
values2.put(MapPoints.LAYER_ID, layerID);
operations2.add(ContentProviderOperation.newInsert(MapPoints.CONTENT_URI).withValues(values2).build());
}
getContentResolver().applyBatch(MapElements.AUTHORITY, operations);
did you override the bulkInsert method in your ContentProvider?

If one insert fails, your whole transaction fails. Without seeing your table create statement for unique keys, try a replace after your insert fails.. Also your numInserted will always be the same as values.length no matter what insert/replace fails. this doesnt seem correct either.
...
db.beginTransaction();
int numInserted = 0;
try {
for (ContentValues cv : values) {
long newID;
try {
newID = database.insertOrThrow(table, null, cv);
} catch (SQLException ignore) {
newID = database.replace(table, null, cv);
}
if (newID <= 0) {
Log.e("TAG, "Failed to insert or replace row into " + uri);
} else {
// you are good...increment numInserted
numInserted++;
}
}
db.setTransactionSuccessful();
getContext().getContentResolver().notifyChange(uri, null);
} finally {
db.endTransaction();
}
return numInserted;

SQLite "database schema has changed" error in Content Provider

I'm using Content Providers and Sync Adapters for my synchronization routine.
My routine receives a JSONObject and insert or update the entry.
In order to decide if we are going to update or insert we check if the entry exists in the database. This is where the sqlite error occurs.
06-03 10:58:21.239: INFO/Database(340): sqlite returned: error code = 17, msg = prepared statement aborts at 45: [SELECT * FROM table WHERE (id = ?) ORDER BY id]
I have done some research and found this discussion about the subject. From this discussion I understand that sqlite_exec() has to be called. How would I implement this in a Content Provider?
Edit
Insert / Update check
// Update or Insert
ContentValues cv = new ContentValues();
/* put info from json into cv */
if(mContentResolver.update(ClientsProvider.CONTENT_URI, cv, null, null) == 0) {
// add remote id of entry
cv.put("rid", o.optInt("id"));
mContentResolver.insert(ClientsProvider.CONTENT_URI, cv);
}
ContentProvider::update
#Override
public int update(Uri uri, ContentValues values, String selection, String[] selectionArgs) {
int count = 0;
switch(uriMatcher.match(uri)) {
case CLIENTS:
count = clientDB.update(TABLE_NAME, values, selection, selectionArgs);
break;
case CLIENT_ID:
count = clientDB.update(TABLE_NAME, values, ID + " = " + uri.getPathSegments().get(0) + (!TextUtils.isEmpty(selection) ? " AND (" + selection + ')' : ""), selectionArgs);
break;
default:
count = 0;
}
return count;
}

Problem is solved. I'm not sure why but after an emulator image wipe everything works exactly how its supposed to do. Thank you for your time Selvin!