I'm building an app where a user can follow other users and be followed.
A user can also look at who another user is following.
Now lets say user1 is looking at who user2 is following, I need to find all the people IDs that user2 is following and compare it against who user1 is following.
Instead of returning only the IDs of all the users that match both user1 and user2 (which I've seen in other forums), I need to retrieve all user2's following IDs and User Names as well as a flag that indicates if the followed person is also followed by user1.
I've got it to work in PHP with a double for loop of each Query, but I worry that this code will be expensive and would be far better optimized with a single MYSQL query.
Relevant tables and columns:
following_table
follower_id
followed_id
following: varchar -- 'true' or 'false'
user_table
user_id
user_name
Here is my PHP code:
$user_id1 = '1991';
$myFollowingQuery = "SELECT following_table.followed_id, user_table.user_name
FROM following_table
INNER JOIN user_table ON
following_table.followed_id = user_table.user_id
WHERE following_table.following = 'true'
AND following_table.follower_id = '$user_id1'";
$user_id2 = '1985';
$userFollowingQuery = "SELECT following_table.followed_id, user_table.user_name
FROM following_table
INNER JOIN user_table ON
following_table.followed_id = user_table.user_id
WHERE following_table.following = 'true'
AND following_table.follower_id = '$user_id2'";
$userFollowingResult = mysql_query($userFollowingQuery)
or doResponse('error',"Couldn't connect to the database");
$myFollowingResult = mysql_query($myFollowingQuery)
or doResponse('error',"Couldn't connect to the database");
for($i = 0; $i< mysql_num_rows($userFollowingResult);$i++){
$loopArray = array(followed_id => mysql_result($userFollowingResult,$i,"followed_id"),
followed_name => mysql_result($userFollowingResult,$i,"user_name"));
for($j = 0; $j< mysql_num_rows($myFollowingResult);$j++){
if(mysql_result($userFollowingResult,$i,"followed_id")
==mysql_result($myFollowingResult,$j,"followed_id")) {
$loopArray['is_following'] = 'true';
break;
}
if($j==mysql_num_rows($myFollowingResult)-1){
$loopArray['is_following'] = 'false';
break;
}
}
$resultArray[$i] = $loopArray;
}
echo json_encode($resultArray);
Here is a simplified query:
http://sqlfiddle.com/#!2/6b8d6/3
SELECT
user.user_id,
user.user_name,
he.follower_id AS follower_id,
IF(me.followed_id,1,0) AS metoo
FROM following AS he
INNER JOIN user
ON user.user_id = he.followed_id
LEFT JOIN following AS me
ON me.follower_id = 1
AND me.followed_id = he.followed_id
WHERE he.follower_id = 2
Related
I am trying to obtain results for a given member where status is pending or accepted doing the below:
$status1 = "Pending";
$status2 = "Attended";
$query = $conn->prepare('SELECT * FROM members WHERE member_id=:mID AND status=:status1 OR status=:status2');
$query->execute(array(':mID' => $mID,':status1' => $status1, ':status2' => $status2));
if ($query->rowCount() > 0) {
//start to create my table
while ($row = $query->fetch(PDO::FETCH_ASSOC)) {
//create variable, loop through and fill the table etc
}
}else{
echo "something";
}
This displays data - however, it even obtains results not specific to the member id (mID). Meaning other members data too!
I'm clearly missing something and or my query is wrong but struggling to find anything..
Any help appreciated.
You need to look at operator precedence for your database. You're doing this:
SELECT * FROM members WHERE member_id = :mID AND status = :status1 OR status = :status2;
Which most likely results in this:
SELECT * FROM members WHERE (member_id = :mID AND status = :status1) OR status = :status2;
But that's not what you want, so you will have to explicitly use parens like this:
SELECT * FROM members WHERE member_id = :mID AND (status = :status1 OR status = :status2);
Alternatively, you can use IN so that there's no OR:
SELECT * FROM members WHERE member_id = :mID AND status IN (:status1, :status2);
SELECT apntoken,deviceid,created
FROM `distribution_mobiletokens` as dm
WHERE userid='20'
and not exists (
select 1
from `distribution_mobiletokens`
where userid = '20'
and deviceid = dm.deviceid
and created > dm.created
)
What this query does is selects all mobiletokens where the user id is equal to 20 and the deviceid is the same but chooses the newest apntoken for the device.
My database looks like below.
For more information on this query, I got this answer from another question I asked here(How to group by in SQL by largest date (Order By a Group By))
Things I've Tried
$mobiletokens = $em->createQueryBuilder()
->select('u.id,company.id as companyid,user.id as userid,u.apntoken')
->from('AppBundle:MobileTokens', 'u')
->leftJoin('u.companyId', 'company')
->leftJoin('u.userId', 'user')
->where('u.status = 1 and user.id = :userid')
->setParameter('userid',(int)$jsondata['userid'])
->groupby('u.apntoken')
->getQuery()
->getResult();
//#JA - Get the list of all the apn tokens we need to send the message to.
foreach($mobiletokens as $tokenobject){
$deviceTokens[] = $tokenobject["apntoken"];
echo $tokenobject["apntoken"]."\n";
}
die();
This gives me the incorrect response of
63416A61F2FD47CC7B579CAEACB002CB00FACC3786A8991F329BB41B1208C4BA
9B25BBCC3F3D2232934D86A7BC72967A5546B250281FB750FFE645C8EB105AF6
latestone
Any help here is appreciated!
Other Information
Data with SELECT * FROM
Data after using the SQL I provided up top.
You could use a subselect created with the querybuilder as example:
public function selectNewAppToken($userId)
{
// get an ExpressionBuilder instance, so that you
$expr = $this->_em->getExpressionBuilder();
// create a subquery in order to take all address records for a specified user id
$sub = $this->_em->createQueryBuilder()
->select('a')
->from('AppBundle:MobileTokens', 'a')
->where('a.user = dm.id')
->andWhere('a.deviceid = dm.deviceid')
->andWhere($expr->gte('a.created','dm.created'));
$qb = $this->_em->createQueryBuilder()
->select('dm')
->from('AppBundle:MobileTokens', 'dm')
->where($expr->not($expr->exists($sub->getDQL())))
->andWhere('dm.user = :user_id')
->setParameter('user_id', $userId);
return $qb->getQuery()->getResult();
}
I did this for now as a temporary fix, not sure if this is best answer though.
$em = $this->em;
$connection = $em->getConnection();
$statement = $connection->prepare("
SELECT apntoken,deviceid,created
FROM `distribution_mobiletokens` as dm
WHERE userid=:userid
and not exists (
select 1
from `distribution_mobiletokens`
where userid = :userid
and deviceid = dm.deviceid
and created > dm.created
)");
$statement->bindValue('userid', $jsondata['userid']);
$statement->execute();
$mobiletokens = $statement->fetchAll();
//#JA - Get the list of all the apn tokens we need to send the message to.
foreach($mobiletokens as $tokenobject){
$deviceTokens[] = $tokenobject["apntoken"];
echo $tokenobject["apntoken"]."\n";
}
I am trying to select users who don't have post in the forum list. For that I wrote a query like this
users_id = Post.where(:forum_id => 1).collect { |c| c.user_id }
#users = User.where('topic_id = ? and id not in ? ', "#{#topic.id}", "#{users_id}")
This code throws mysql error, and in my log
SELECT `user`.* FROM `user` WHERE (forum_id = '2222' and id not in '[5877, 5899, 5828, 5876, 5841, 5838, 5840, 5882, 5881, 5870, 5842, 5843, 5844, 5845, 5889, 5896, 5869, 5847, 5849, 5850, 5855, 5857, 5859, 5867, 5861, 5863, 5865, 5868, 5829, 5830, 5831, 5832, 5833, 5900, 6326, 6326, 6332, 5898, 6333, 6334, 6335, 6336, 6339, 7034, 7019, 6336, 5887, 5827, 9940, 9943, 9949, 7030, 9979, 9980, 5892, 9896, 14208, 14224, 14281, 14282, 14283, 5894, 5895, 14689, 14717]'
In mysql I execute the following query, and got the expected result
select * from users where topic_id = 1 and id not in (select users_id from posts where forum_id = 1);
The above query in rails doesn't seem to work..
Try this:
users_ids = Post.where(:forum_id => 1).collect { |c| c.user_id }
#users = User.where('topic_id = ? and id not in (?) ', #topic.id, users_ids)
Also, I advice you to make some changes:
Use pluck instead of collect (pluck is on the DB level)(pluck doc ; pluck vs. collect)
users_ids = Post.where(:forum_id => 1).pluck(:user_id)
name the table in the where clause to avoid ambiguous calls (in where chaining for example):
User.where('users.topic_id = ? AND users.id NOT IN (?)', #topic.id, users_ids)
The final code:
users_ids = Post.where(:forum_id => 1).pluck(:user_id)
#users = User.where('users.topic_id = ? AND users.id NOT IN (?)', #topic.id, users_ids)
i'm writing a chat app with php/mysql
i have 3 tables: user, room and room_participant with these structures:
user: id, username
room: id, title
room_participant: room_id, user_id
Now i want to get list of all rooms along with list of all participants in each room.
Until now i just select all rooms from room table and iterate through all rooms and select users information out of each entry, which is very inefficient.
Is there any way to combine all these select into only 1 select query?
Not certain about this without testing, but give it a try:
SELECT
room.*,
user.*
FROM room
JOIN room_participant ON room_id = room_participant.id
JOIN user ON room_participant.user_id = user.id
ORDER BY room.id
To deduplicate rooms, use GROUP_CONCAT()
UPDATE GROUP_CONCAT() modified to return id|username
SELECT
room.id, room.name
GROUP_CONCAT(CONCAT(user.id,'|',user.username)) AS userlist
FROM room
JOIN room_participant ON room_id = room_participant.id
JOIN user ON room_participant.user_id = user.id
GROUP BY room.id, room.name
ORDER BY room.id
With the userlist generated by GROUP_CONCAT as id|name,id|name,id|name you can use PHP explode() to separate them.
// Split the list on the commas
$users = explode(",", $userlist);
$final_users = array();
// Then split each on the `|`
foreach ($users as $user) {
$split_user = explode("|", $user);
// Append each as a new associative array to $final_users
$final_users[] = array('id' => $split_user[0], 'username' => $split_user[1]);
}
// Now you have an array of users as id, username
var_dump($final_users);
You may wish to do two queries, and then match things up in whatever is using MySQL, e.g. PHP.
These two:
SELECT id, title
FROM room;
SELECT rp.room_id, rp.user_id, u.username
FROM room_participant AS rp
INNER JOIN user as u ON rp.user_id = u.id;
Or these two:
SELECT id, username
FROM user;
SELECT rp.room_id, rp.user_id, r.title
FROM room_participant AS rp
INNER JOIN room as r ON rp.user_id = r.id;
Which two queries make sense depends on what you're doing with the info really.
You could go a step further and select all three separately:
SELECT *
FROM room;
SELECT *
FROM user;
SELECT *
FROM room_participant;
Note: It's probably better to state the columns, rather than using '*', just in case in the future new columns are added to the table that you're not really interested in for these queries.
Obviously, you'd then have to match everything up in whatever is using MySQL, e.g. PHP. You could create a list of rooms and users from the selected info, and then match them up with something like:
// Use MySQL to populate $roomList from database, then do...
foreach ($roomList as $room)
{
$id = $room['id'];
$title = $room['title'];
$this->roomList[$id] = new Room($id, $title);
}
// Use MySQL to populate $userList from database, then do...
foreach ($userList as $user)
{
$id = $user['id'];
$username = $user['username'];
$this->userList[$id] = new User($id, $username);
}
// Use MySQL to populate $roomParticipantList from database, then do...
foreach ($roomParticipantList as $roomParticipant)
{
$room = $this->roomList[$roomParticipant['room_id']];
$user = $this->userList[$roomParticipant['user_id']];
// You could do one/both of these, depending on requirements.
$room->enterUser($user);
$user->joinRoom($room);
}
Is it possible to merge these queries?
$sql1 = "UPDATE users AS u, invites AS i
SET u.uinvite = u.uinvite - 1, u.ufriends = CONCAT(u.ufriends, ',$iid'), i.seen = 1
WHERE u.uid = '$uid' AND i.invited_uid = '$uid' AND i.invitor_uid = '$iid'";
$sql2 = "UPDATE users
SET ufriends = CONCAT(ufriends, ',$uid')
WHERE uid = '$iid'";
Variable explanation:
$uid = the users ID $iid = the friends ID
This was my attempt to merge:
$mergesql = "UPDATE invites AS i, users AS u
SET
CASE
WHEN u.uid = '$uid' THEN u.uinvite=u.uinvite-1, u.ufriends = CONCAT(u.ufriends,',$iid')
ELSE u.ufriends = CONCAT(u.ufriends,',$uid')
END
, i.seen = '1'
WHERE i.invited_uid = '$uid' AND i.invitor_uid = '$iid'
AND (u.uid = '$uid' OR u.uid = '$iid')"
I find it hard to understand how mysql works when you have to do more complicated queries.
My English also lacks expertise, if you know a good tutorial, you can make me really happy with it! (not the one from the MySQL website, it's killing =S)
Knowing MySQL, there is probably a way to do this in one query, but I don't think you would get any benefit at all because you are updating based on totally separate keys. It might actually be dangerous to do this because the result would be unpredictable. Doing it in two queries, it's easy to figure out what's going on.
If it's not too late, I would suggest that you remove the friends field in favor of a mapping table between users and friends.
Did you try this:
$mergesql = "UPDATE
users AS u,
invites AS i,
users AS uf
SET
u.uinvite = u.uinvite - 1, u.ufriends = CONCAT(u.ufriends, ',$iid'),
i.seen = 1,
uf.ufriends = CONCAT(uf.ufriends, ',$uid')
WHERE u.uid = '$uid'
AND i.invited_uid = '$uid' AND i.invitor_uid = '$iid'
AND uid = '$iid'";
?