Here's what I came up with but I'm not sure which one of these is "the best". Perhaps there's another, better one that I may not know of. Keep in mind that I have both inbox and outbox in my app and messages deleted by either sender or recipient should still be visible to other related users unless they delete it themselves.
Option 1 - simple ManyToMany:
Tables:
User - just user fields
Message - just message fields
User_Message - contains 2 foreign keys: user_id and message_id
Example: When user sends a message, ONE message row is added to the Message table, and TWO rows are added to User_Message, obviously connecting sender and recipient with the added message. Now, this might get a little problematic when let's say I want to fetch only inbox messages because ManyToMany will fetch all of them so I came up with option 2.
Option 2 - OneToMany:
Tables:
User - just user fields
MessageReceived - message fields AND foreign key to user_id
MessageSent - message fields AND foreign key to user_id
Example: When user sends a message, this message is added to both received and sent tables but with different user_id. Of course senders id will be in sent table and recipient id in received table.
Now, when I want to fetch only inbox messages, I'm fetching messages from MessageReceived table and while deleting for example inbox (MessageReceived) message, copy of it still stays in MessageSent and is available to sender so everything is fine, however I feel like there's something "not cool" about this one because I'm basically keeping ALMOST the same data in both tables.
Please, let me know what do you think about this and if there is any better way to do it, I'm also listening.Thanks for your time.
EDIT :
Both Madbreaks and Tab Alleman provided really good and somewhat similar solutions so thanks for that. I'm gonna go with Madbreaks one, simply because I prefer to delete the relations in join table instead of keeping a 'deleted' column but that's just my taste. Nevertheless, thank you both for your time and answers.
You shouldn't need to add 2 rows in user_messages for each message - have 3 columns in that table: sender_id, recipient_id, message_id.
EDIT
The deletion scenario you describe in your question, below, changes things. Instead of a n-to-n approach, you likely now have two 1-to-n relationships:
the relationship between sender and their many sent messages
the relationship between a recipient and their many received messages
I would probably have the messages table have a sender ID foreign key. I would then have a message_recipients table that maps user (recipient) ID to message ID.
Now, if a sender can delete a message but the recipients should still be able to access it (and know who the sender is), then you'll need four tables:
users
messages
message_sender (1-to-1 map) -- senders deleting sent messages deletes from her
message_recipients (1-to-n map) -- recipients deleting received messages deletes from here
It's not clear from your question whether or not this is a requirement, I only add it for completeness. You may want a trigger or a subsequent query to determine if/when there are no remaining relationships between the users and messages tables, and at that time (possibly) delete the message itself.
Here's what I would do (I am assuming a message can only have one sender, but multiple recipients)
UserTable - Contains UserID and Other info
MessageTable - Has MessageID, SenderID (FK to UserTable.UserID) and other info
MessageRecipientsTable - Has MessageID, RecipientID (FK to UserTable.UserID), and possibly other info like when/if it was received, etc.
If you want a recipient to be able to delete a message and still have it show for the sender (and other recipients), then you would add a "Deleted" column to the MessageRecipientsTable. You would never actually delete a row from the messages table, but when populating a recipients inbox you would filter out the rows where "Deleted" is true.
Related
I am currently trying to create an email style web app to allow users of my site to contact one another. I have created an SQL table for this, which has the following headings:
id
senderID
recipientID
timestamp
message
read (Boolean to record whether message has been read by recipient)
starred (Boolean to record whether message has been starred by recipient)
archived (Boolean to record whether message has been archived by recipient)
deleted (Boolean to record whether message has been deleted by recipient)
convoID
I have started to now realise that this table is insufficient. For example, if the conversation has been starred by a user, this does not tell me which of the 2 users has starred the convo, etc.
Can anyone suggest a way to avoid the above issue, and maybe suggest a better database structure?
I would recommend split your table into two, let's call them "message" and "star". So, they are:
message
-------
id
sender_id
recipient_id
timestamp
read
archived
deleted
convo_id
parent_id
star
----
message_id
user_id
timestamp
As you can see, I added parent_id into message. If you don't need hierarchical structure - you may kick this column. A star table gives possibility to enhance starring feature. Who knows, maybe in future all users may put a star, not only participants of conversation.
In addition, there is a nice articles about DB normalization. It will really helps you to build well-organized DB structure:
What is Normalisation (or Normalization)?
http://www.studytonight.com/dbms/database-normalization.php
http://searchsqlserver.techtarget.com/definition/normalization
depend on your application and how many users you will have.
About the starred, archived and other stuff where both users can do things, you can use an enumeration or simply a couple of values. Not just a boolean.
Or you can split every read with a senderRead and recipentRead
I've a SQL table which contains all the users and groups conversation in it. I'm able to retrieve group conversation from it easily but don't know how to retrieve last messages of each user from it.
Explanation of columns:
• message_id: Self explanatory
• group_id: Since the conversation also contains group messages, I'll use group_id to filter those messages instead of creating a new messaging table for it.
• user: Sender/Receiver (It can be both sender or receiver by defining the value on last column 'isReceived').
• message: Self explanatory
• creation: Self explanatory
• isSeen: If the message has been seen by the user (receiver).
• isError: If there was an error while sending the message.
• isReceived: To check whether the message was received or send by the default user.
Now what I really want is to retrieve last messages of all conversations no matter if its sent or received. Example, 'Sondre' (Another User) sent me a message "Hi" and now I sent him a reply/message "Hello" and when I retrieve data from messages table I want my reply to be shown instead of his. I've also uploaded photos of current data and the data using query I want:
Data of messages table:
Data I want using query:
You need to do it in two parts first get the latest messages, grouped by user
Then fetch your messages against these
Simplest answer is (it would work fine if you really have message_id a unique/primary key)
select * from messages where message_id in
(select max(message_id) from messages group by user)
It will give you the latest message from each user, Yo can also group by other things instead of user
The better version you need (for better performance with scalability) is
select messages.* from messages
join
(select max(creation) maxtime,user from messages group by user) latest
on messages.creation=latest.maxtime and messages.user=latest.user;
Abvove will work even if you do not have a unique/primary key column like message_id, but if you really have it then i would recommend to use message_id instead of creation
you can see implemented SQL Fiddle Demo
For a project that I am on, on of the requirements is users being able to send each other friend requests and either accepting them or declining them.
Side note: the project is built on Laravel.
At first my data model for those friendships was as such (leaving out things as timestamps etc. in this example):
pivot_friend_request
====================
sender_id
receiver_id
status
Of course sender_id and receiver_id have a foreign key constraint to id on the user table.
Here I ran into this case issue:
CASE:
User foo invites bar (table row: foo-bar-pending)
Meanwhile user bar never reads his notifications but searches user foo
User bar invites user foo (table row: bar-foo-pending)
Now I have two table rows for those two users that have sent friend requests to each other that are both pending.
What is the best way to check if foo-bar is already present before also inserting bar-foo (regardless of the request status)?
Then I asked my project manager what do to, resulting in him asking me why I was going about it like this. To have a more object oriented approach he told me to have separate tables for the requests and actual friendships because a request is a request and a friendship is a friendship.
I think he made a good point there but it confused me even more. Because:
Now I have to deal with the above mentioned case twice and I still don't have a solution to it.
Plus it made me think on how to handle the request table. Should the request be removed from it after accepting or should there still be a status of the request?
Can it be more efficient like this because I now see it like this:
Request is sent by bar
Check if foo-bar already exists in request table
If exists update pending to accepted else create new one with pending. (If already accepted return 'Already friends message')
Create new row in friendship table
Also... what if a friendship gets removed? I know have two tables where I should update that status? The request and the actual friendship table?
I really really need some pointers here it seems.
if friendship get removed you have to update both request and friendship table. for example,
bar invites foo.then in request table you can set statusas pending
once foo accepts the friend request add row to a friends table.
later foo unfriends bar. then friend table will be updated.
now bar wants to invite foo again. butbar cannot send a new friend request to foo since there is already a record in the request table. so you have to update request table at the 3rd step or 2nd step.
however this whole scenario depends on your requirements.
The communication between Facebook users seem to be stored in one long "conversation." So, emails sent and private chat messages exchanged all seem to be part of one long ongoing conversation.
I think this implementation works well for users (at least it does for me). I assume the table design for this part could be implemented this way:
TABLE: message
- message_id
- timestamp
- from_user_id
- to_user_id
- message
What if I wanted to support group chat? Would I do something like this:
TABLE: message
- message_id
- timestamp
- from_user_id
- message
TABLE: message_recipient
- message_recipient_id
- message_id
- to_user_id
I think it'll work. However, I'm wondering if it would make sense to the user if I displayed every single things that user has ever messaged anyone in one long conversation. It probably wont. Imagine a conversation with Person A mixed with group conversation with Person A, B, C, D mixed with conversation with Person E and so on ....
Any suggestion on what would be a usable concept to implement?
I believe a message should be an entity, regardless of platform or sender/receiver, with id,message,timestamp fields, and a message relation table - like you suggested - with id,message_id,from_id,to_id.
Then, if you are showing a single user to user conversation, you can show every message between them.
For group chats, you should have a table with id,title,timestamp that holds the group chat main record, and another table that holds the users that are part of that group chat, with id,group_chat_id,user_id fields.
Just my opinion and how I would implement it.
Edit: Maybe it would make sense to have from_id on the message entity itself, as a message has to have a singular sender id.
You could also group messages by topics.
You add a topic table. You add a recipients table, tied to a topic. Messages will also be tied to a topic.
You can programmatically limit the topics between two users by looking which topic has those two users in its recipients.
You could also separate your messages by giving them a type attribute. For example, type 0 will be an inbox message, type 1 will be a chat message and so on.
If I wanted to have an arbitrary number of recipients in one topic, I would avoid the from_id/to_id combo.
I am just trying to figure out how Facebook's database is structured for tracking notifications.
I won't go much into complexity like Facebook is. If we imagine a simple table structure for notificaitons:
notifications (id, userid, update, time);
We can get the notifications of friends using:
SELECT `userid`, `update`, `time`
FROM `notifications`
WHERE `userid` IN
(... query for getting friends...)
However, what should be the table structure to check out which notifications have been read and which haven't?
I dont know if this is the best way to do this, but since I got no ideas from anyone else, this is what I would be doing. I hope this answer might help others as well.
We have 2 tables
notification
-----------------
id (pk)
userid
notification_type (for complexity like notifications for pictures, videos, apps etc.)
notification
time
notificationsRead
--------------------
id (pk) (i dont think this field is required, anyways)
lasttime_read
userid
The idea is to select notifications from notifications table and join the notificationsRead table and check the last read notification and rows with ID > notificationid. And each time the notifications page is opened update the row from notificationsRead table.
The query for unread notifications I guess would be like this..
SELECT `userid`, `notification`, `time` from `notifications` `notificationsRead`
WHERE
`notifications`.`userid` IN ( ... query to get a list of friends ...)
AND
(`notifications`.`time` > (
SELECT `notificationsRead`.`lasttime_read` FROM `notificationsRead`
WHERE `notificationsRead`.`userid` = ...$userid...
))
The query above is not checked.
Thanks to the idea of db design from #espais
You could add another table...
tblUserNotificationStatus
-------------------------
- id (pk)
- notification_id
- user_id
- read_status (boolean)
If you wanted to keep a history, you could keep the X latest notifications and delete the rest that are older than your last notification in the list....
If, when you give notifications, you give all relevant notifications available at that time, you can make this simpler by attaching timestamps to notifiable events, and keeping track of when each user last received notifications. If you are in a multi-server environment, though, you do have to be careful about synchronization. Note that this approach doesn't require true date-time stamps, just something that increases monotonically.
I see no-one here addresses the fact, that notifications are usually re-occurring, aka. notification of an upcoming transaction is always going to be the same, but with a different transaction ID or Date in it. as so: { You have a new upcoming payment: #paymentID, with a due date of #dueDate }.
Having texts in a different table can also help with
If you want to change the notification text later on
Making the app multilingual is easier, because I can just layer the notifications table with a language code and retrieve the appropriate string
Thus I also made a table for those abstract notifications, which are just linked under the the user with a middle table, where one notification type can be sent to one user at multiple times. I also linked the notifications to the user not by a foreign key ID, but I made notification codes for all notifications and full_text indexed the varchar field of those codes, for faster read speeds. Due to the fact that these notifications need to be sent at specific times, it is also easier for the developer to write
NotificationService::sendNew( Notification::NOTE_NEW_PAYMENT, ['paymentId'] => 123, ['dueDate'] => Carbon::now(), 'userIdToSendTo' );
Now since my messages are going to have custom data in them, that is inserted into the string, as you can see from the second argument beforehand, then I will store them in a database blob. as such
$values = base64_encode(serialize($valuesInTextArray));
This is because I want to decouple the notifications from other tables and as such I dont want to crete unnessecary FK relations from and to the notifications table, so that I can for example say notification 234 is attached to transaction 23 and then join and get that transaction ID. Decoupling this takes away the overhead of managing these relations. The downside is, it is nigh impossible to delete notifications, when for example a transaction is deleted, but in my use case I decided, this is not needed anyway.
I will retrieve and fill the texts on the App side as follows. Ps. I am using someones vksprintf function (https://github.com/washingtonpost/datawrapper/blob/master/lib/utils/vksprintf.php), props to him!
$valuesToFillInString = unserialize(base64_decode($notification->values));
vksprintf( $notificationText->text, $valuesToFillInString )
Notice also which fields I index, because I am going to find or sort by them
My Database design is as follows
==============================
TABLE: Users
id (pk)
==============================
TABLE: Notifications
id (pk)
user_id (fk, indexed)
text_id (fk - NotificationTexts table)
values (blob) [containing the array of values, to input into the text string]
createdDateTime (DateTime)
read (boolean)
[ClusterIndex] => (user_id, createdDateTime)
==============================
TABLE: NotificationTexts
id (pk)
text_id (uniquem indexed)
text (varchar) [{ You have a new upcoming payment: #paymentID, with a due date of #dueDate }]
note (varchar, nullable) [notes for developers, informational column]
I am also trying to figure out how to design a notification system. Regarding notification status (read, unread, deleted, archived, ect) I think that it would be good a good candidate to for ENUM. I think it is possible that there will be more than two different types of status other than READ and UNREAD such as deleted, archived, seen, dismissed, ect.
That will allow you to expand as your needs evolve.
Also I think it may make sense (at least in my case) to have a field to store an action url or a link. Some notifications could require or prompt the user to follow a link.
It also may make sense to have a notification type as well if you want different types. I am thinking there could be system notifications (such as a verify email notification) and user prompted notifications (such as a friend request).
Here is the structure I think would be a minimum to have a decent notification system.
users
-------------
id
username
password
email
notifications
-------------
id
user_id (fk)
notification_type (enum)
notification_status (enum)
notification_action (link)
notification_text
date_created (timestamp)
Table are following
User
userId (Integer)
fullName(VarChar)
Notification
notificationId (Integer)
creationDate (Date)
notificationDetailUrl (VarChar)
isRead (bollean)
description (VarChar)
userId (F.K)