[英]cascade delete in android room database KOTLIN
There are a bunch of questions like this in StackOverflow but most of that arent about room database, so I had to ask a new question. StackOverflow 中有很多这样的问题,但大部分都不是关于房间数据库的,所以我不得不问一个新问题。
I have an app that uses room database and that has near 4 tables and a big relationship between those tables, so for instance when I delete a user in user list fragment, that user delete(only userName and some personal info) but the user's TRANSACTIONS and LOANS hadn't been deleted.我有一个使用房间数据库的应用程序,它有近 4 个表并且这些表之间的关系很大,所以例如当我在用户列表片段中删除一个用户时,该用户删除(只有用户名和一些个人信息)但用户的 TRANSACTIONS并且LOANS没有被删除。 Someone told me I have to use Cascade delete but I didn't find much info about it.
有人告诉我我必须使用Cascade delete ,但我没有找到太多关于它的信息。
My User class model:我的用户 class model:
@Entity(tableName = "user_info")
data class UserInfo(
@PrimaryKey(autoGenerate = true)
@ColumnInfo(name = "user_id")
var userId: Long =0L,
@ColumnInfo(name = "full_name")
var fullName:String?,
@ColumnInfo(name= "account_id")
var accountId: String?,
@ColumnInfo(name = "mobile_number")
var mobileNumber:String?,
@ColumnInfo(name = "phone_number")
var phoneNumber:String?,
@ColumnInfo(name = "date_of_creation")
var dateOfCreation:String?,
@ColumnInfo(name = "address")
var address:String?,
)
Transactions model class:事务 model class:
@Entity(tableName = "transactions")
data class Transactions(
@PrimaryKey(autoGenerate = true)
@ColumnInfo(name = "trans_id")
var transId: Long = 0L,
@ColumnInfo(name = "user_id")
var userId: Long?,
@ColumnInfo(name = "create_date")
var createDate: String?,
@ColumnInfo(name = "bank_id")
var bankId: Long?,
@ColumnInfo(name = "description")
var description: String?,
@ColumnInfo(name = "increase")
var increase: String?,
@ColumnInfo(name = "decrease")
var decrease: String?,
@ColumnInfo(name = "loan_number")
var loanNumber: String?,
@ColumnInfo(name = "total")
var total: Long?,
@ColumnInfo(name = "type")
var type: String?
)
User DAO:用户 DAO:
@Insert
suspend fun insert(ui: UserInfo): Long
@Update
suspend fun update(ui: UserInfo)
@Insert
suspend fun insertList(ui: MutableList<UserInfo>)
@Delete
suspend fun deleteUser(ui: UserInfo)
@Query("DELETE FROM user_info")
fun deleteAllUser()
@Query("SELECT user_info.user_id, user_info.full_name, transactions.total From user_info JOIN transactions ")
fun joinTable(): LiveData<List<UserAndMoney>>?
@Query("SELECT * from user_info WHERE user_id = :key")
fun get(key: Long): LiveData<UserInfo>?
@Query("SELECT * FROM user_info ORDER BY full_name DESC")
fun getAllUserInfo(): LiveData<List<UserInfo>>
@Query("SELECT * FROM user_info where full_name like '%' || :fullName || '%' ORDER BY full_name ASC")
fun searchUserName(fullName: String): LiveData<List<UserInfo>>
If It was not clear for you till now, let me makes it easy for you:如果到目前为止您还不清楚,让我为您简单介绍一下:
I need cascade delete that delets every thing about user and a record.我需要级联删除来删除有关用户和记录的所有内容。
CASCADE is an option of a Foreign Key constraint. CASCADE 是外键约束的一个选项。 So you would need to define Foreign Key constraints.
所以你需要定义外键约束。 You define Foreign Key constraints in Room via the @Entity annotation.
您可以通过 @Entity 注释在 Room 中定义外键约束。
As an example, as it would appear that a Transactions is related to a UserInfo via var userId: Long?,
(column name user_id) you could have:-例如,看起来事务通过
var userId: Long?,
(column name user_id) 与 UserInfo 相关,您可以:-
@Entity(tableName = "transactions",
foreignKeys = [
ForeignKey(
entity = UserInfo::class,
parentColumns = ["user_id"],
childColumns = ["user_id"],
onDelete = ForeignKey.CASCADE, //<<<<<
onUpdate = ForeignKey.CASCADE // Optional
)
]
)
data class Transactions(
@PrimaryKey(autoGenerate = true)
@ColumnInfo(name = "trans_id")
var transId: Long = 0L,
@ColumnInfo(name = "user_id", index = true) // <<<<< best to have an index on the column, not required
var userId: Long?,
@ColumnInfo(name = "create_date")
var createDate: String?,
@ColumnInfo(name = "bank_id")
var bankId: Long?,
@ColumnInfo(name = "description")
var description: String?,
@ColumnInfo(name = "increase")
var increase: String?,
@ColumnInfo(name = "decrease")
var decrease: String?,
@ColumnInfo(name = "loan_number")
var loanNumber: String?,
@ColumnInfo(name = "total")
var total: Long?,
@ColumnInfo(name = "type")
var type: String?
)
Note笔记
The constraint enforces referential integrity, that is a transaction can not be inserted/updated if the user_id value is not a value that exists in the user_id column of the user_info table.约束强制引用完整性,即如果 user_id 值不是 user_info 表的 user_id 列中存在的值,则无法插入/更新事务。
The CASCADE onUpdate will cascade a change to the user_id value in the user_info table to the respective transactions. CASCADE onUpdate 将对 user_info 表中的 user_id 值的更改级联到相应的事务。
Someone told me I have to use Cascade delete but I didn't find much info about it.
有人告诉我我必须使用 Cascade delete,但我没有找到太多关于它的信息。
You could replicate the functionality without CASCADE.您可以在没有 CASCADE 的情况下复制该功能。
In short you could use简而言之,您可以使用
@Query("DELETE FROM transaction WHERE user_id=:userId")
fun cascadeDeletionsFromUser(userId: Long)
cascadeDeletionsFromUser
function would have to be run before the user_info row is deleted.cascadeDeletionsFromUser
操作,则必须在删除 user_info 行之前运行 cascadeDeletionsFromUser function。 Otherwise the user_info row could not be deleted as the FK constraint would inhibit the deletion.
声明:本站的技术帖子网页,遵循CC BY-SA 4.0协议,如果您需要转载,请注明本站网址或者原文地址。任何问题请咨询:yoyou2525@163.com.