I have created a room database, and showed my data in a RecyclerView. I know how to add, delete, deleteAll, update data in room data base, but the problem is I don't know how to perform search in room data base?
I have added a search view in the tool bar. But I don't know how to add Queries in NoteDao and the remaining classes, e.g. in my adpter, MainActivity etc.
If you're able to show your Room database in the RecyclerView, this would mean you should know how to use the #Query() tag for fetching your data.
Searching is done using the same #Query tag using the WHERE keyword.
For example, if you wish to find a specific note:
#Query("SELECT * FROM notes WHERE id == :id")
public Note getNote(String id)
However, that's just the simplest way to use WHERE. Frequently, you'll be combining it with other keywords such as IN, LIKE, or BETWEEN.
So for your situation of using a search, you would most likely want to use the LIKE keyword, which can query your database for a field that contains parts of its data that matches the search criteria:
For example:
#Query("SELECT * FROM notes WHERE note_title LIKE :search OR note_message LIKE :search")
public List<Note> getSearchedNote(String search)
This would search your database and return a list of Notes that has either a Note Title or a Note Message that contains the search term you want.
Related
I am trying to implement a Room database using a one-to-many relation, following the Android Room training (https://developer.android.com/training/data-storage/room/relationships#one-to-many).
However, I can't find a way to add a condition on the second table.
For example, to fetch all UserWithPlaylists, for users above 25 and having playlists names starting with "play" this does not work because Room does not automatically group the results (and a GROUP BY clause prevents creating the List of Playlist):
#Transaction
#Query("SELECT User.* FROM User, Playlist WHERE User.age > 25 AND Playlist.playlistName LIKE play%")
public List<UserWithPlaylists> getUsersWithPlaylistsSpecific();
I already tried solutions such as embedding one entity in another and using
#Embedded(prefix = "PETS_")
as suggested here: https://stackoverflow.com/a/50698610 but without success.
I also want to avoid this method using a Java Map.
How can I achieve this?
So I have a room database all set up, everything is fine, so I can make queries and inserts, delete etc no problems, however i've just run into a situation where id like to return entries by their Ids and duplicates should be allowed, however room is removing the duplicates, so for instance I send it a list of ids say <1,2,3,2,3> and it returns items by their ids but only sends me <1,2,3> removing the duplicate entries. The query I'm making is below (btw complete noob at sql)
#Query("SELECT * FROM card WHERE cardId IN(:cardId)")
LiveData<List<Card>> getCardsByIds(List<Integer> cardId);
Im using it via a repository I created (just a level of abstraction) and calling this repo from a ViewModel, this ViewModel has a mutable live data integer list containing the ids and using a SwitchMap I get the latest live data. ill include the relevant pieces below
CARD REPO calls my Daos method like this
public LiveData<List<Card>> getCardsByIds(List<Integer> cardIds){
return cardDao.getCardsByIds(cardIds);
}
ViewModel calls for them
private MutableLiveData<List<Integer>> cardIds;
//** constructor etc
cards = Transformations.switchMap(cardIds, id -> cardRepository.getCardsByIds(id));
and through the magic of SwitchMap when the cardIds list updates a new query is made and I observe the ViewModel from my fragment. I've debugged it so I know the list of Ids is correct and has the duplicates Ids, but the returned LiveData list is missing the duplicate Ids. any help?
Edit:
The SQLiteDatabase always presents the results as a Cursor in a table format that resembles that of a SQL database.
Source : Google Developer Training
Before the results are returned by the query, the results are stored in a table, and if there are rows with duplicate primary keys, they would be omitted by default.
To achieve what you intend, you can execute a query to find single element by id in loop and append the result to a list.
Updated DAO method:
#Query("SELECT * FROM card WHERE cardId=:cardId")
LiveData<Card> getCardById(Integer cardId);
Update Repository method:
public LiveData<List<Card>> getCardsByIds(List<Integer> cardIds){
List list = new ArrayList();
for(Integer cardId: cardIds){
list.append(cardDao.getCardById(cardId));
}
return list;
}
Hope this helps.
Original Answer:
If id is the primary key of your model, It doesn't allow duplicate data to be entered. Hence while retrieving you might find duplicates missing.
If you have id with duplicate, create another attribute for primary key. (use autogenerate if you don't have any primary key attribute)
A primary key is by default UNIQUE and NOT NULL.
Question
Is it possible to dynamically build the filtering for a query?
The problem
I have a big list, addresses. The user can filter it with typing text in a SearchView. If the user put any space in the text it will be divided and the two part of the text will be searched separately. I have to build the SQL dynamically because I didn't know how many space characters will be. Is there any way to handle this in Room whit simple #Query or I have to use #RawQuery for this?
Example SQL for this:
SELECT * FROM ADDRESS WHERE (CITY LIKE '%abc%' OR STREET LIKE '%abc%') AND (CITY LIKE '%abc%' OR STREET LIKE '%def%') AND (....)
I think what you should do is use RawQuery.
Since your query is complicated and you are not sure how long it is, you should probably construct it in runtime and execute it as well.
Room check the validity of the #Query in compile time so I think you'll have a hard time to implement it that way.
This example is taken from the documentation:
#Dao
interface RawDao {
#RawQuery
User getUserViaQuery(SupportSQLiteQuery query);
}
SimpleSQLiteQuery query = new SimpleSQLiteQuery("SELECT * FROM User WHERE id = ? LIMIT 1", new Object[]{userId});
User user2 = rawDao.getUserViaQuery(query);
You can pass those words in an array
#Query("SELECT * FROM ADDRESS WHERE CITY LIKE(:keywords)") //customize your query here
List addresses(String[] keywords);
Is it possible to use SQLite's IN condition with Room?
I'm trying to select a list of items from my database where the value of a certain column (in this case a TEXT column) matches any one of a set of filter values. That's pretty easily done in SQL and SQLite, by my knowledge, just by adding an IN condition to your SELECT statement (see here). However, I can't seem to make it work with Room.
I keep getting this error:
Error:(70, 25) error: no viable alternative at input 'SELECT * FROM Table WHERE column IN :filterValues'
(where the input to the DAO #Query-annotated method is called filterValues)
I have tried three different methods now:
Passing the argument as a List<String>
Passing the argument as a String[]
And lastly passing the argument as simply a String, but formatted as (value_1, value_2, ..., value_n)
The last one in particular should work easily, as it will (or at least, it should) directly translate to SELECT * FROM Table WHERE column IN (value_1, value_2, ..., value_n), which is the exact way you would manually write out the SELECT if you were just accessing the database directly.
So as I was preparing to submit this, I double-checked a bunch of the stuff I had looked up previously and found the thing I had somehow missed and would have saved this question from being necessary.
As it turns out, both of these options:
Passing the argument as a List<String>
Passing the argument as a String[]
are viable (and you can replace String with any type the database can represent, such as char or int), you simply need to change the syntax in the #Query annotation from this:
#Query("SELECT * FROM Table WHERE column IN :filterValues")
to this:
#Query("SELECT * FROM Table WHERE column IN (:filterValues)")
Easy as pie, right?
Note that the third method above (passing the argument as simply a String, but formatted as (value_1, value_2, ..., value_n)) does not appear to be supported by Room, but that's probably not a bad thing, since that's the hard way.
Since I already had the whole thing typed out, I figured I would leave the question up in case other people are have as much difficulty finding this solution as I did and stumble upon this question.
Hi you can use this query:
#Query("SELECT * FROM user WHERE uid IN(:userIds)")
public abstract List findByIds(int[] userIds);
or
#Query("SELECT * FROM user WHERE uid IN(:userIds)")
public abstract List findByIds(List<Integer> userIds);
Similarly to above answers in Kotlin you can use vararg instead of array or list:
#Query("SELECT * FROM user WHERE uid IN (:userIds)")
fun getUsers(vararg userIds: Int): List<User>?
and use it like repository.getUsers(1, 2, 3).
If needed, to convert vararg to list see https://proandroiddev.com/kotlins-vararg-and-spread-operator-4200c07d65e1 (use *: format(output, *params)).
I am designing an Android app with a fairly complex (normalized) database structure. My question is, what is the best design pattern for working with my data?
The database has a table Books, a table Authors, a table Collections (of books), and a junction table Books_Collections that relates the two based on an integer ID. I say that it is fairly complex because I want to display a list of books & authors in a specific a collection in a ListView in format "Book Title (Author Name)", so I need to be able to perform the following query (I will abbreviate the table names A, B, C, and B_C):
SELECT B.title, A.name
FROM B
JOIN A ON B.author_id = A.id
JOIN B_C ON B_C.book_id = B.id
WHERE B_C.collection_id = [variable]
I have seen some people advising developers to wrap their Sqlite databases in a Content Provider to easily take advantage of the Loaders introduced in Honeycomb. But is this really feasible for such complex queries? (If so, how?) or would it be better to just use DAO since I am not sharing my data with other apps? And if using DAO, should a custom AsyncTaskLoader be created to connect the data to a ListView?
EDIT
One more important detail: I want to change the background color of the list items based on a boolean variable in Books marking whether or not the book has been read, and a context menu will allow users to delete books from the list, so the list needs to adjust instantly to data changes.
Yes, is doable and easily done
I'm no expert but im followin the pattern used by google on his Google I/O app
https://code.google.com/p/iosched/
Check the provider package where u have the 3 classes needed for using the pattern
ScheduleDatabase.java
(definition of sqlite3 database)
ScheduleProvider.java
(Content provider atttached to this database)
ScheduleContract.java
(Contract defined to expose the provider)
Personally, in the case of join
in the Database File i define
interface Tables {
String TABLE1= "table1";
String TABLE2= "table2";
// JOINS
String TABLE1_JOIN_TABLE2 = "table1"
+ "LEFT OUTER JOIN table2 ON table1.table_id= table2.tableid";
}
and then in your provider map a provider entity to this join.
I ended up using database helpers/adapters and creating a custom AsyncTaskLoader. I wasn't able to find a ton of examples of custom ones, and there's not great documentation on it, but it's not too hard to figure out. Works like a charm.