single SQL Query to fetch results from tables with Many-Many relationship - php

i have a table named IMAGES in which there is attribute name img_ID which is the primary key,
there is another table called Favorites in which there are two attributes 'img_ID' & user_ID ... img_ID serves as the foreign key to an image and user_ID serves as foreign key to the user
NOW i need details of from IMAGES of all the img_IDs from Favorites where user_ID is some x-value
this i could do like this, b.t.w i am using PHP & mySQL
$gett = mysql_query("SELECT img_ID FROM favorites WHERE user_ID='".$variable."'");
if( mysql_num_rows($gett) > 0 )
{
while( $steps = mysql_fetch_assoc($gett) )
{
$res = mysql_query("SELECT * FROM images WHERE img_ID='".$steps['img_ID']."' ORDER BY img_Date");
if( mysql_num_rows($res) > 0 )
{
while( $result= mysql_fetch_assoc($res) )
{
echo $result['img_Name'];
echo $result['img_Desc'];
echo $result['img_ext'];
}
else
echo "no images were found";
}
}
else
echo "no favorites were found";
THE PSEUDO CODE will be like
RUN QUERY
for each img_ID where user_ID is this
RUN QUERY
for each img_ID
perform DISPLAY
This methodology has a flaw & a back-draw
FLAW = the order which is on time stamp is destroyed
back-draw = there is a query in nested loop..
QUESTION: Can this all be done in with query? if Yes then How ?

Use a join:
select
i.*
from
favorites f
join images i on f.img_id = i.img_id
where
f.user_id = <user id>
Also, change your code to use mysqli and prepared statements with bind variables to both improve performance and eliminate the threat of sql injection attacks.

SELECT i.* -- possibly would need to be "SELECT DISTINCT i.*" instead
FROM images AS i
INNER JOIN favorites AS f
ON f.img_ID = i.img_ID
WHERE f.user_ID = ???

No loops, just query both tables.
SELECT
images.*
FROM
images
INNER JOIN
favorites
ON
favorites.img_ID = images.img_ID
WHERE
favorites.user_ID = X

Related

Select a fixed number of records from a particular user in a sql result

I have 2 tables - users and articles.
users:
user_id (int)
name (varchar)
articles:
article_id (int)
user_id (int)
title (varchar)
description (text)
In my application I need to display 20 RANDOM articles on a page.
My query is like this:
SELECT a.title
, a.description
, u.name
FROM articles a
JOIN users u
USING (user_id)
ORDER
BY RAND()
LIMIT 20
A user can have any number of articles in the database.
Now the problem is sometimes out of 20 results, there are like 9-10 articles from one single user.
I want those 20 records on the page to not contain more than 3 (or say 4) articles from a particular user.
Can I achieve this through SQL query. I am using PHP and MySQL.
Thanks for your help.
You could try this?
SELECT * FROM
(
SELECT B.* FROM
(
SELECT A.*, ROW_NUMBER() OVER (PARTITION BY A.USER_ID ORDER BY A.R) USER_ROW_NUMBER
FROM
(
SELECT a.title, a.description, u.name, RND() r FROM articles a
INNER JOIN users u USING (user_id)
) A
) B
WHERE B.USER_ROW_NUMBER<=4
) C
ORDER BY RAND() LIMIT 20
Mmm, intresting I don't think this is possible through a pure sql query.
My best idea would be to have an array of the articles that you'll eventually display query the database and use the standard SELECT * FROM Articles ORDER BY RAND() LIMIT 20
The go through them, making sure that you have indeed got 20 articles and no one has breached the rules of 3/4 per user.
Have another array of users to exclude, perhaps using their user id as an index and value of a count.
As you go through add them to your final array, if you find any user that hits you rule add them to the array.
Keep running the random query, excluding users and articles until you hit your desired amount.
Let me try some code (it's been a while since I did php)
$finalArray = [];
$userArray = [];
while(count($finalArray) < 20) {
$query = "SELECT * FROM Articles ";
if(count($finalArray) > 0) {
$query = $query . " WHERE articleID NOT IN(".$finalArray.")";
$query = $query . " AND userID NOT IN (".$userArray.filter(>4).")";
}
$query = $query . " ORDER BY Rand()";
$result = mysql_query($query);
foreach($row = mysql_fetch_array($result)) {
if(in_array($finalArray,$row) == false) {
$finalArray[] = $row;
}
if(in_array($userArray,$row[userId]) == false) {
$userArray[$row[userId]] = 1;
}
else {
$userArray[$row[userId]] = $userArray[$row[userId]] + 1;
}
}

How to optimize nested query with PHP and MySqli?

I have this code, that fetches data from two tables in MySQLi.
It first has to get the title, description, status and project_id from table 1, and then get the name from table 2 using the id from table 1.
Is there a better/faster way to do this? I have about 600 rows in the tables, and it takes about 5 sec to run this query. I will also add that this example is a bit simplified, so please don't comment on the db-structure.
<?php
$results = $connect()->db_connection->query(
'SELECT title, description, status, project_id
FROM table
WHERE created_by ='.$user_id
);
if ($results) {
while ($result = $results->fetch_object()) {
$res = $connect()->db_connection->query(
"SELECT name FROM projects WHERE id = ".$result->project_id
);
if ($res) {
while ($r = $res->fetch_object()) {
echo $r->name;
}
}
echo $result->title;
echo $result->status;
}
}
?>
Use Query:
SELECT title,description,status,project_id
FROM table tb
inner join projects pr on pr.id = tb.project_id
WHERE created_by = $user_id
Try to use JOIN in your query.
You can find examples and description of this command here: http://www.w3schools.com/sql/sql_join.asp
Check out also this infographics:
http://www.codeproject.com/KB/database/Visual_SQL_Joins/Visual_SQL_JOINS_orig.jpg
You can use JOIN on project_id:
$results = $connect()->db_connection->query('SELECT t.title title,t.description,t.status status,t.project_id, p.name name FROM `table` t JOIN projects p ON p.id= t.project_id WHERE t.created_by ='.$user_id);
if($results){
while($result = $results->fetch_object()){
echo $result->name;
echo $result->title;
echo $result->status;
}
}
tables have aliases here - t for table and p for projects.
Also to make it faster, add index to project_id in table table, if you haven't done it yet:
$connect()->db_connection->query('ALTER TABLE `table` ADD INDEX `product_id`');

MySQL/PHP - Nested Select Issue - Need To Obtain Values From Both Tables

I just need help refining this script to give me the values from both tables joined on the ID.
Basically I want the ID from both tables and then be able to get the other values from both tables based on the IDs (if need be) and display them in a loop.
The code I have is below but won't work.
$select = myQ("SELECT * FROM users a WHERE EXISTS (SELECT 1 FROM `videos` b WHERE a.id = b.id GROUP BY b.id HAVING count(*) > 1) ");
$i=0;
while ($row = myF($select)) {
$resultsLoopArray[$i]["videos.id"] = $row["id"];
$resultsLoopArray[$i]["videos.vid"] = $row["vid"];
$resultsLoopArray[$i]["users.username"] = $row["username"];
$i++;
}
if (isset($resultsLoopArray)) {
$tpl->Loop("searchResultsLoop", $resultsLoopArray);
}
For now all I need is the username from the users table, the id and video id from the video table.
Can someone help by chance?
you question is bit confusing me..
As for my understanding I am posting this soultion..
If you have two tables users , videos then .
$sql = "SELECT users.username , videos.* from users, videos where users.user_id = videos.user_id";
this query will fetch all record from users and videos table where user id is present in videos tables ...

combining 2 mysql queries into 1

i am having trouble creating a single mysql query for what i am trying to do here.
first off, i will show you the table structures and fields of the tables i am using for this particular query:
users:
- id
- name
- photo_name
- photo_ext
user_attacks:
- id
- level
user_news_feed:
- id
- id_user
- id_status
- id_attack
- id_profile
- id_wall
- the_date
user_status:
- id
- status
user_wall:
- id
- id_user
- id_poster
- post
whenever the user posts an attack, or status update, updates their profile, or posts on someones wall, it inserts the relevant data into its respective table and also inserts a new row into the user_news_feed table.
now, what i want to do is select the last 10 news feed items from the database. these news feed items need to grab relevant data from other tables as long as their value is not 0. so if the news feed is for a status update, the id_status would be the id of the status update in the user_status table, and the "status" would be the data needing to be selected via a left join. hope that makes sense.
heres my first mysql query:
$sql = mysql_query("select n.id_user, n.id_status, n.id_attack, n.id_profile, n.id_wall, n.the_date, u.id, u.name, u.photo_name, u.photo_ext, s.status
from `user_news_feed` as n
left join `users` u on (u.id = n.id_user)
left join `user_status` s on (s.id = n.id_status)
where n.id_user='".$_GET['id']."'
order by n.id desc
limit 10
");
now this works great, except for 1 problem. as you can see the user_wall table contains the id's for 2 different users. id_user is the user id the post is being made for, and id_poster is the user id of the person making that wall post. if the user makes a wall post on his/her own wall, it is inserted into the database as a status update into the user_status table instead.
so i have a conditional statement within the while loop for the first query, which has another sql query within it. here is the whole code for the while loop and second sql query:
while ($row = mysql_fetch_assoc($sql))
{
if ($row['id_wall'] != 0)
{
$sql_u = mysql_query("select u.id, u.name, u.photo_name, u.photo_ext, w.post
from `user_wall` as w
left join `users` u on (u.id = w.id_poster)
where w.id='".$row['id_wall']."'
");
while ($row_u = mysql_fetch_assoc($sql_u))
{
$row['photo_name'] = $row_u['photo_name'];
$row['photo_ext'] = $row_u['photo_ext'];
$row['id_user'] = $row_u['id'];
$row['name'] = $row_u['name'];
$content = $row_u['post'];
}
}
else
{
if ($row['id_status'] != 0)
$content = $row['status'];
else if ($row['id_attack'] != 0)
$content = '<i>Had an attack</i>';
else if ($row['id_profile'] != 0)
$content = '<i>Updated profile</i>';
}
echo '<li'.(($count == $total_count) ? ' class="last"' : '').'>';
echo '<img src="images/profile/'.$row['photo_name'].'_thumb.'.$row['photo_ext'].'" alt="" />';
echo '<div class="content">';
echo '<b>'.$row['name'].'</b>';
echo '<span>'.$content.'</span>';
echo '<small>'.date('F j, Y \a\t g:ia', $row['the_date']).'</small>';
echo '</div>';
echo '<div style="clear: both;"></div>';
echo '</li>';
}
i hope what i am trying to do here makes sense. so basically i want to have both sql queries ($sql, and $sql_u) combined into a single query so i do not have to query the database every single time when the user_news_feed item is a wall post.
any help would be greatly appreciated and i apologise if this is confusing.
SELECT n.id_user, n.id_status, n.id_attack, n.id_profile, n.id_wall, n.the_date,
u.id, u.name, u.photo_name, u.photo_ext, s.status,
w.id AS wall_user_id, w.name AS wall_user_name,
w.photo_name AS wall_user_photo_name,
w.photo_ext AS wall_user_photo_ext,
w.post
FROM user_news_feed AS n
LEFT JOIN users AS u ON (u.id = n.id_user)
LEFT JOIN user_status s ON (s.id = n.id_status)
LEFT JOIN (SELECT a.id AS id_wall, b.id, b.name, b.photo_name, b.photo_ext, a.post
FROM user_wall AS a
LEFT JOIN users AS b ON (b.id = a.id_poster)
) AS w ON w.id_wall = n.id_wall
WHERE n.id_user = ?
ORDER BY n.id desc
LIMIT 10
The '?' is a placeholder where you can provide the value of $_GET['id'].
Basically, this adds an extra outer join, to the main query (and some extra columns, which will be NULL if the news feed event is not a wall posting), but the outer join is itself the result of an outer join.
Back again ;)
Anyway, forget about merging the queries in my opinion.
What you should do instead is to do the first query, loop through all the results and store all "id_wall"s in a separate array... then rather than doing a separate query per "id_wall" you do this:
$wallids = array();
while ($row = mysql_fetch_assoc($sql))
{
$wallids[] = $row['id_wall'];
// also store the row wherever you want
}
$sql_u = mysql_query("select u.id, u.name, u.photo_name, u.photo_ext, w.post
from `user_wall` as w
left join `users` u on (u.id = w.id_poster)
where w.id IN ('".implode(',', $wallids) ."')
");
$wallids being an array with all the "id_wall"s. So now you have a total of 2 queries.

Help construct a simple query Using 3 tables

Hey guys need some more help
I have 3 tables USERS, PROFILEINTERESTS and INTERESTS
profile interests has the two foreign keys which link users and interests, they are just done by ID.
I have this so far
$statement = "SELECT
InterestID
FROM
`ProfileInterests`
WHERE
userID = '$profile'";
Now I want it so that it selects from Interests where what it gets from that query is the result.
So say that gives out 3 numbers
1
3
4
I want it to search the Interests table where ID is = to those...I just don't know how to physically write it in PHP...
Please help.
Using a JOIN:
Best option if you need values from the PROFILEINTERESTS table.
SELECT DISTINCT i.*
FROM INTERESTS i
JOIN PROFILEINTERESTS pi ON pi.interests_id = i.interests_id
WHERE pi.userid = $profileid
Using EXISTS:
SELECT i.*
FROM INTERESTS i
WHERE EXISTS (SELECT NULL
FROM PROFILEINTERESTS pi
WHERE pi.interests_id = i.interests_id
AND pi.userid = $profileid)
Using IN:
SELECT i.*
FROM INTERESTS i
WHERE i.interests_id IN (SELECT pi.interests_id
FROM PROFILEINTERESTS pi
WHERE pi.userid = $profileid)
You are on the right track, lets say you execute the query above using this PHP code:
$statement = mysql_query("SELECT InterestID FROM `ProfileInterests`
WHERE userID = '$profile'");
Then you can use a PHP loop to dynamically generate an SQL statement that will pull the desired IDs from a second table. So, for example, continuing the code above:
$SQL = "";
while ($statementLoop = mysql_fetch_assoc($statement)) {
//Note the extra space on the end of the query
$SQL .= "`id` = '{$statementLoop['InterestID']}' OR ";
}
//Trim the " OR " off the end of the query
$SQL = rtrim($SQL, " OR ");
//Now run the dynamic SQL, using the query generated above
$query = mysql_query("SELECT * FROM `table2` WHERE {$SQL}")
I haven't tested the code, but it should work. So, this code will generate SQL like this:
SELECT * FROM `table2` WHERE `id` = '1' OR `id` = '3' OR `id` = '4'
Hope that helps,
spryno724
Most likely you want to join the tables
select
i.Name
from
ProfileInterests p
inner join
interests i
on
p.interestid = i.interestid
where
p.userid = 1

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