this is a example:
User and Orders. 1:N relation
but UserDAO do not have a method called "setOrders(List...)"
only getOrdersList() and resetXXXList()
You have to do it from the other part of the relation, Orders, using something like order.setUser(user) and updating the entity in the DB.
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?
I am using Room Database for storing chat, I have one group table and I want to fetch three parameters like this query
My Group Entity class is GroupUserEntity.kt
#Query("SELECT DISTINCT group_id, group_name, group_image FROM group_user_table")
fun getAllGroups() : List<ENTITY_CLASS>
I am not able to use my Group Entity class(GroupUserEntity.kt) over ENTITY_CLASS, forcefully I have to make new Entity class(Pojo Class) to fetch those three values.
So my questions is, there is any way to utilize my old Entity class(GroupUserEntity.kt) to fetch all groups? or I need to make a new POJO class for that?
It depends on number of variables in your GroupUserEntity.kt.
If for example you have group_id, group_name, group_image and group_category (total 4) in GroupUserEntity.kt and you are fetching data for only 3 variables then it will show you an error. (Cursor mismatch).
To avoid this either call ALL the columns values from database to match GroupUserEntity.kt, or create a new POJO.
I just started using Room library for database and I figured out that it is more complicated to put an object in the table. I made a diagram to demonstrate the situation in my app:
I could insert the Workout object into my table, but I have to create Converters to simplify the Exercise List object.
I also would like to create a table for Exercises that have the Workline List objects..
Any suggestions?
Thanks in advance.
I am using Realm database. I have an average of five models. I want to call all the models when I search. Is it possible?
ClassOne
ClassTwo
ClassThree
ClassFour
ClassFive
When querying is not one by one as follows.
RealmResult<ClassOne> list = realm.where(ClassOne.class).equelsTo("key", "a").findAll();
what kind of query I can make calls in all models?
you can't do this because every query return a RealmResuts of the type used on "Where"
The documentation says:
Returns a typed RealmQuery, which can be used to query for specific objects of this type
https://realm.io/docs/java/latest/api/io/realm/Realm.html#where-java.lang.Class-
I have entityA and entityB that have a one-one relationship between them (entityA.a = entityB).
My question is: if I set entityA.a = entityB, then insert entityA, will entityB automatically be inserted?
I think it should be, but it looks like it's not.
Does that mean I should insert entityB myself?
By the way, I know I should call insert myself for a one-to-many relationship.
No, it won't be inserted. A relation is a link between two existing entities, you should first insert both entities and set de relation after.