update multiple tables in Android Room Database

Question

I have two models

Types Model

@Entity(tablename="tbl_types")
data class Types(
@PrimaryKey(autoGenerate = true)
    val typesId:Int,
    val name: String?,
    val posts:List<Post>?))

PostModel

@Entity(tablename="tbl_post")
data class Post(
@PrimaryKey(autoGenerate = true)
    val postId:Int,
    val name: String?,
    val details:String?))

A post can be a part of different types so when I change the post's data like name or details I want to update all the types that have this specific post in its posts column. How do I do that?. Do I have to update the type table manually? I don't quite know how the foreign key works and if it will let me update the item on the list or not.

Answer 1

Ok Room support Embedded objects in an entity so lets make Post embedded in Type like this:

@Entity(tablename="tbl_types")
data class Types(
@PrimaryKey(autoGenerate = true)
    val typesId:Int,
    val name: String?,
    @Embedded val posts:List<Post>?))

now for updating the post you easily just change the desired post in the list, in the Type Model and you just need to say:

@Update
fun updateType(type: Types)

and that's the power of Room for updating a row easily. Hope it Helps.

Answer 2

Not containing Post in Type table. Create third table to save the relateion of post and type.

@Entity(tablename="tbl_types")
data class Types(
@PrimaryKey(autoGenerate = true)
    val typesId:Int,
    val name: String?)

@Entity(tablename="tbl_post")
data class Post(
@PrimaryKey(autoGenerate = true)
    val postId:Int,
    val name: String?,
    val details:String?))

@Entity(tablename="type_post_relation", primaryKeys =
    ["postId","typeId"])
data class PostTypeRelation(
    val postId:Int,
    val typeId: Int,
)

...
@Query("UPDATE Tour SET typeId = :toTypeId WHERE postId = :postId and typeId = : fromTypeId")
fun updatePostType(postId: Int, fromTypeId: Int, toTypeId: Int)

The relation table uses postId and typeId to be primary key. When changing post type, just update relation table with a postId and typeId. And if you want to query all posts in one specific type, you can use sql to combine query, so querying post's types.