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I have taken it on myself to create a site that allows users to add each other as friends and comment on each others posts. After looking into this I'm not sure exactly how to start. I have a posts and a users table.
My question is how would I relate the databases to
1.Check if user A has sent a friend request to user B?
2.Store a value to indicate that they are friends?
I've browsed around this site before posting but can't seem to understand how to carry this out. Pretty sure I'm just over complicating it. Could anyone explain the concept or how this works?
This could be done with a relational database, and it would be worth reading up on how relational databases work e.g. https://www.youtube.com/watch?v=NvrpuBAMddw
But - to give some pointers, it looks like yor want your relational database to allow for the following functions:
a number of users
a series of posts, by certain users
a number of relationships between users
an ability to verify a relationship before it is confirmed
a series of posts, by certain users
a number of 'sub-post' comments on posts
1) Let's start with the 'friend request' section.
This would need you to have a) a whole load of different users, and b) a load of relationships between those users.
You'd need to represent that in 2 different tables - so create a users table with the following fields:
UserID, name, age, [details, password, address etc etc]
and then a friends table which has these fields:
friendID, userID1, userID2, [date, confirmed]
Your user table might look like this:
UserID, name, age,
1 Fred 18
2 George 24
3 Michael 20
4 Alice 24
5 Sophie 20
6 George 19
Let's say that Michael wants to become friends with Alice and Fred, and Alice wants to befriend Sophie - you'd want to create records in your friends table that looked like this:
FriendID, userID1, userID2,
1 3 (this refers to Michael) 4 (this refers to Alice)
2 3 (this refers to Michael) 1 (this refers to Fred)
3 4 (this refers to Alice) 5 (this refers to Sophie)
So if you then looked for Michael's friends - you'd do a query which looked for:
every record from the friend table where userID1 = Michael's userID.
From the userID2 field, you'd get userID 4 and userID 1
By looking up those userids in the user table, you'd find more details for Alice and Fred.
You should make this query check whether userID1 OR userid2 = the userID you need, so that you get the same results if e.g. the table looked slightly differently:
FriendID, userID1, userID2,
1 3 (this refers to Michael) 4 (this refers to Alice)
2 1 (this refers to Fred) 3 (this refers to Michael)
3 4 (this refers to Alice) 5 (this refers to Sophie)
Otherwise you'd only know about Alice.. but you want to know about Fred too.
2) If you want to confirm a relationship, you could add a 'confirmed' field to the friends table - set it to binary 0 = not confirmed / 1 = confirmed.
When the friendship is requested, you add the record to the table, but when it is confirmed, you would update the 'confirmed' field for that record to 1.
Let's update our friends table accordingly:
FriendID, userID1, userID2, confirmed
1 3 (Michael) 4 (Alice) 0
2 3 (Michael) 1 (Fred) 1
3 4 (Alice) 5 (Sophie) 1
If you want to see all friends that are pending Michael's acceptance, you'd search for:
any records from the friends table where userid1 = 3
AND confirmed = 0 ... which means it hasn't been accepted yet.
This would show that alice hasn't yet been accepted as a friend by Michael.
If you want to see all friends a user had requested but which haven't been accepted you'd look for:
any records from the friends table where userid2 = the user you're looking for
AND confirmed = 0 ... which means it hasn't been accepted yet.
If you want to see all accepted friends, switch 'confirmed' to 1.
3) You also wanted to have posts for each user... so you'll need a posts table with fields for:
postid, userid, date, content
We've already got your user table, so let's say that Michael wanted to post some stuff. The posts table might look like this:
postid, userid, date content
1 3 (Michael) [auto datetime] Hi everyone
2 3 (Michael) [auto datetime] This is my second post
You've now got a relationship between Michael and the posts table. If another user posted something, they'd add another line with a different userid. You can then retrieve all the posts from the posts table where the userid = 3, which is Michael's userid.
4) To add comments on posts you would need a comments table that might look like this:
commentid, postid, userid content
1 1 3 (Michael) Michael is commenting on his own first post...
2 2 4 (Alice) Alice is saying something on Michael's second post
Related
Table one
Id subject class teacher
1 English 1 1
2 Math 1 2
3 SST 1 3
4 Computer 1 1
5 Physics 1 3
6 Chemistry 1 3
Each subject assigned to particular teacher, some subject has same teacher.
Now i want to store values in another table having these fields and other fields as well.
Table Two
id subject teacher
Whereas form only post subject ids, how can i get teacher id against each subject id from Table one and store it in table two?
Your question is very unclear. Are you asking for how to use relational databases and foreign keys? If so I would read up on how a relational database works and that will answer your question. If the question is about how to do this in code then please state that and also post your attempt at it.
What i think you want to do is get the of the subject posted, i.e. query the database :
SELECT subject, teacher FROM table_one WHERE id = 'POSTED_ID'
Then insert the new record into the table two, something like :
INSERT INTO table_two (subject, teacher) VALUES ('subject_value', 'teacher_value')
Hope this helps!
I want to create an up vote and down vote system for my website where a unique user can vote up/down for one post and next time he only allow to opposite to get off from database and after that he again can up or down vote.
In this case I have:
users table :
id
name
debates table :
id
post
upvotes table:
id
user_id
debate_id
and similarly downvote table:
id
user_id
debate_id
Is that a good way to manage and track up vote and down vote concept?
I think, you can use a single table to track the votes and the structure could be something like this
Table : votes
id | user_id | debate_id | vote
Here, vote field could be tinyInt with defauld null.
And, in vote field, you just keep two different values depending on the vote type, for example, if a user up votes then insert a value of 1 in the vote field and for down vote, insert the value of 0. So, your table may look something like this
id | user_id | debate_id| vote
1 | 10 | 4 | 1 <-- up
2 | 11 | 4 | 0 <-- down
3 | 12 | 4 | 1 <-- up
In this case, two users with id = 10 and id = 12 up voted the post whose debate_id = 4 and another user with user_id = 11 down voted on the same post.
IN this case, you may find out how many up or down votes a post got by counting the vote field's value, for example, you may count for up votes for debate_id = 4 using something like this
$count = Debate::where('debate_id', '=', 4)->where('vote', '=', 1)->count();
Also, you may use something Query Scope, this is just an idea and it's not possible to make an answer which covers everything in this scope. You should start using some basic idea and if you stuck at a certain point, then you may ask specific questions with your code.
Also, I would like to mention that, if you find a user id in the votes table with a certain debate_id then this user has voted on this post and to find out the vote type, just check the vote field 1 or 0.
I would prefer to only have one table containing the votes, this could be done with an extra column such as is_downvote int(1).
It seems that you havn't tried much which is always a negative. For this scenario the Laravel Eloquent Documentation should be plenty to figure this out.
I would of written this as a comment but it's pretty lengthy now.
I am working on an application with PHP + MySql. In my application I have a table for users, a table for relationships (friends, following, subscribed) and a table for posts. The main actions for users are:
A user has friends
A user can make post entries
A user can see the friends entries
And finally a user can block entries viewing for specific friends
If user A is friends with user B, then user A can see all entries from user B. But user B can restrict access to only a few friends for example. Now the query is: how can I manage these permissions? I was thinking of a table that stores each user that is blocked for viewing an specific entry, but this would't be a good idea once a single user can have several friends. So, how can I solve this? Can someone show me how to start? Maybe the right terms for searching on Google or a link for something similar.
You are on the right track. You are going to want to use linked tables. You would start with a table users. Each user has an id. Then create a table users_friends. This table would consist of two ids, user_id and friend_id. The last table would be users_restricted which would also consist of two ids, user_id and restricted_id.
For example
users
user_id name
1 user1
2 user2
3 user3
users_friends
friend1_id friend2_id
1 2
2 3
This says user 1 and 2 are friends and users 2 and 3 are friends. (This assumes that if user 1 is friends with user 2 then user 2 is also friends with user 1)
users_restricted
user_id restricted_id
1 2
Now even though user 1 and user 2 are friends, user 2 is in the restricted list meaning don't allow user 2 to view user 1's entries.
You can see that tables are linked via ids and all the ids come from the users table. This can be expanded to relate to entries as well. Just refer to entries by their id.
To have users blocked for specific entries you would have the following tables.
entries
entry_id user_id ... other columns holding entry information
1 1
2 1
3 2
4 2
Now user 1 has made 2 entries (entry 1 and entry 2) and user 2 has made 2 entries (entry 3 and entry 4). Another table would hold the restrictions.
entries_restricted
entry_id restricted_user_id
1 2
This would say user 2 cannot view entry 1.
To get the entries visible to user 2 your statement would look something like this.
SELECT e.*, er.entry_id FROM entries e JOIN entries_restricted er ON e.entry_id=er.entry_id WHERE er.restricted_user_id != 2;
The statement selects all the entry information excluding entries restricted to user 2.
You can start using following tables.
The first table is users table (as Jason.Wolfsmith suggested)
users
u_user_id u_name
1 user1
2 user2
3 user3
The second table can be like this.
friends_permissions
f_user_id f_friend_id permission entries
1 2 1 entry1
2 3 0
1 3 1 entry3
This table will contain permission and name of entries that should be allow for view. 1 - restrict some entries; 0 - allow all.
In the column permission data type might be set as SET('1','0') and data type in entries NULL.
Thus, user1 don't allow to view entry1 to user2. (entry1 and entry3 are from entries table).
I'm trying to come up with the most simple / userful / efficient method to group 3 users together using mysql.
To set the stage:
X number of users in a list (all with int account_id's)
mini groupings need to be created on a per user basis (user 1 wants to group with 220 for instance).
Max 3 people per grouping (user 1 + user 220 + user 9123 = group full)
Need to easily find if a user is in a group or not without looking in a bunch of columns
I'm stumped about how best to create a schema for this (so I can easily query my table to see if user is in a group, or if they can be added, or check for group space availability).
Anyone have any idea? My initial thought is schema like this (but it really seems too rigid):
Schema
GROUP_ID USER1 USER2 USER3 LASTUPDATE
1 1 220 null 5/25/2011 20:00:00
2 300 2 4 5/25/2011 20:00:00
How would you do it to make something this simple very flexible and efficient. I really feel stupid for asking.
Personally I would approach this by using 3 tables.
Users Table
user_id user_name ..... last_update
Groups Table
group_id group_name ......
Users to groups Table
user_to_group_id user_id group_id
This forms a many to many relationship by linking through the "Users to groups" table, obviously you can have more that 3 users linked to one group so you will have to make your PHP logic check for this when adding a new user to a group.
You can simply use SQL joins to retrieve all the data required and filter the results in your PHP code.
I hope this helps
Kind regards
Garry
I've got an small issue, I'm trying to make my own forum, but I am stuck at something.
I have 3 tables, 1 users with a user_level (Authentication level).
forum_section which contains all the sections with a user_level again.
But how can I link forum_section.user_level to forum_topics.user_level.
So if I define: forum_section.user_level = 4 for forum_section.section_id = 1.
For example:
Someone wants to visit the forum_section id 1 then they must have a auth level of 4.
And when they go to the topic it then again checks if the user level is 4, but I do not want to manual set the topic level, topic level must always be the same as the section level.
I've googled for this, but I can't really find a good manual for it. I guess it has something to do with: "foreign keys"?
Okay, let me explain a bit more just to be sure.
I have 3 tables
Table User
username = Wesley
userlevel < for example 4(admin).
Table section
section_id = 3
section_name = News
section_level = 3 <require level to view.
table topics
topic_id = 123
topic_name = I like candy
topic_level = Needs to be the same as section_level so if I change section_level it automatically changes this too.
You should have to manage your database by using master and transaction tables.
Your table format should look like this:
table name: user
user_id user_name
1 abc
2 xyz
3 pqr
4 new
table2 name : forum_section
forum_id user_id forum_name
1 4 abc
2 4 jkl
3 2 cbd
4 3 lmn
Now, you can JOIN these two tables and make a query as you want, like this:
SELECT forum_id FROM forum_section as fs,user as u WHERE fs.user_id = u.user_id AND fs.user_id = 4
This may help you. Please write if you need more help!
You need to either use a SQL JOIN or a NESTED SUB QUERY
The simplest implementation would be to initially establish the users access level, then filter subsequent queries based on this- so in your PHP, pass the access level to subsequent requests for content- if the query returns anything, the user can view the content, if not- they can be redirected.