I have a SELECT query where you search by car owners.
Every owner can have more than one car.
There is random generated list of cars of which we have to find owners.
...
$owners[] = $dbaseowners["ownerid"] // owner ID's fetched from database
$owners = implode (',',$owners);
SELECT carname FROM cars WHERE ownerid IN ($owners);
My problem is when one owner is used more than once for example: IN (1,1,4,1) - mysql only fetch one 'copy' of this owner's data.
Since i have a randomly generated car list, I have to have owner row for every car no matter if owner is the same.
Any ideas?
I believe you have to revise your design and have a join table to relate the owners to cars. Having 1,1,4,1 in one row of table is not compliant with the first normal form and you should avoid using it.
Try using array_unique to remove duplicate values from your array:
...
$owners[] = $dbaseowners["ownerid"] // owner ID's fetched from database
$owners = implode (',', array_unique($owners));
SELECT carname FROM cars WHERE ownerid IN ($owners);
Try this:
$sql = mysql_query("SELECT `ownerid`, `carname` FROM `cars` WHERE `ownerid` IN (".array_unique($owners).")");
$ret = Array();
while($row = mysql_fetch_assoc($sql)) $ret[$row['ownerid']] = $row['carname'];
foreach($owners as $owner) {
echo $owner.": ".$ret[$owner]."<br />\n";
}
Related
How would I go about deleting a row from the table 'subjects' that has a primary id 'subject_id' based on the number of rows in another table named 'replies' that uses a 'subject_id' column as a reference.
Example in pseudo code:
If ('subject' has less than 1 reply){
delete 'subject'}
I don't know much about SQL triggers so I have no clue if I would be able to incorporate this directly in the database or if I'd have to write some PHP code to handle this...
To delete any subjects that have had no replies, this query should do the trick:
DELETE s.* FROM subjects AS s
WHERE NOT EXISTS
(
SELECT r.subject_id
FROM replies AS r
WHERE r.subject_id = s.subject_id
);
Demo: DB Fiddle Example
One of the MySQL gurus will need to weigh in on whether or not you can do this directly, but in PHP you could...
$query = "SELECT subject_id FROM subjects WHERE subject='test'";
$return = mysqli_query($mysqli, $query);
$id = mysqli_fetch_assoc($return);
$query = "SELECT reply_id FROM replies WHERE subject_id='".$id[0]."'";
$return = mysqli_query($mysqli, $query);
if(mysqli_num_rows($return) < 1){
$query = "DELETE FROM subjects WHERE subject_id='1'";
$return = mysqli_query($mysqli, $query);
}
This example assumes the "subject" is unique. In other words, SELECTing WHERE subject='test' will only ever return one subject_id. If you were doing this as a periodic cleaning, you would grab all the subject_id values (no WHERE clause) and loop through them to remove them if no replies.
You can achieve this in one query by selecting all (unique) subject-ids from the replies table, and delete all subjects that doesn't have a reply in there. Using SELECT DISTINCT, you don't get the IDs more than once (if a subject has more than one reply), so you don't get unnecessary data.
DELETE FROM subjects
WHERE subject_id NOT IN (SELECT DISTINCT subject_id FROM replies)
Any subject that doesn't have a reply should be deleted!
So you want to delete all subjects with no replies:
DELETE FROM subjects WHERE subject_id NOT IN
(SELECT subject_id FROM replies);
I think this is what you want...
I have a table named users and has a user_id, and a table named groups and has a group_id and also have user_id that is a foreign key reference from users's user_id.The situation is here: if the user joined a group, his/her user_id is inserted into table groups. So if the user joined two different groups, the column 'user_id' in table 'groups' will insert two or more same user_id's. Well, I just want to bring the user_id once, either he/she joined two or more groups..
I have no idea how to loop it properly without getting user_id that is the same.... I just want it to loop once...
$query_groups = mysql_query("SELECT * FROM groups");
while ($rows_g = mysql_fetch_assoc($query_groups)) {
$g_user_id = $rows_g['user_id'];
$query_users = mysql_query("SELECT * FROM users WHERE user_id='$g_user_id'");
while ($rows_u = mysql_fetch_assoc($query_users)) {
echo $rows_u['user_id'];
}
}
change your code as follows:
$query_groups = mysql_query("SELECT user_id FROM groups LEFT JOIN users ON users.user_id = groups.user_id GROUP BY groups.user_id");
while($rows = mysql_fetch_assoc($query_groups))
{
echo $rows['user_id'];
}
You are using $rows_g but the variable is namend $rows in the first while loop.
Wrong:
$g_user_id = $rows_g['user_id'];
Correct:
$g_user_id = $rows['user_id'];
But try to use joining tables, because this is an inefficient way to get the wanted data.
In your case you should use LEFT JOIN.
I have a table named records with the columns: recordid, artist, album, description and coverimg. Some of the albums in the table have the same artist.
On my site I would like to display it like this:
-artist1
album1
album2
- artist2
album3
-artist3
album4
album5
If I use GROUP BY it just shows one row per artist. Is there any other way to group them without resorting to relational tables?
Because now I have a form to insert and update the table through my site, and I have no idea how I would have to code the forms to make this work with relational tables.
try this
select artist,group_concat(album) from albums group by artist
gives you
artist1 | album1,album2,album3
artist2 | albumx,albumy
You can split the second column in PHP e.g. using explode(row[1])
That should help you a bit
You can do it without a group by:
<?php
$query = 'Select artist, album
FROM records
ORDER BY artist'
$result = mysql_query($query);
$artist = '';
while ($line = mysql_fetch_assoc($result)){
// only show artist when it's an other artist then the previous one
if ($line['artist'] != $artist){
echo $line['artist'].'<br/>';
$artist = $line['artist'];
}
echo $line['album'].'<br/>';
}
?>
I know I should not be using mysql_* functions anymore, please choose mysqli_* or PDO....
I have a table that has patient information (name, dob, ssn, etc.) and a table that has lists of medications that they take. (aspirin, claritin, etc.) The tables are related by a unique id from the patient table. So, it's easy enough to pull all of Mary Smith's medications.
But, what I need to do is to show a paginated list of patients that shows their name, other stuff from the patient table and has a column with a line-separated list of their medications. Roughly, this:
If I do a simple left join, I get 3 repeated rows of Mary Smith with one medication per row.
The patient table can have thousands of records, so I don't want to do a query to get all the patients and then loop through and get their meds. And, because it's paginated based on patient, I can't figure out how to get the correct number of patients for the page, along with all their medications.
(The patients/medications thing is just a rough example of the data; so please don't suggest restructuring how the data is stored.)
GROUP_CONCAT to the rescue!
SELECT patients.first_name, patients.last_name, GROUP_CONCAT(prescriptions.medication SEPARATOR ", ") AS meds FROM patients LEFT JOIN prescriptions ON prescriptions.patient_id = patients.id GROUP BY patients.id;
You've got a few choices.
rowspan clauses with one drug per cell per user. You'd need to run two SQL queries to precalculate how big each user's span would have to be, or suck the query results into PHP and do the counting there.
Simple state machine - start a new row each time the user changes, then just keep adding more drug names seperated with <br /> while the user's name stays constant.
The second one's probably easiest:
$previous_name = null;
$first = true;
echo "<table";
while($row = mysql_fetch_assoc($results)) {
if ($row['name'] <> $previous_name) {
if (!$first) {
echo "</td></tr>"; // end previous row, if it's not the first row we've output
$first = false;
}
echo "<tr><td>$row[name]</td><td>"
$previous_name = $row['name'];
}
echo "$row['drug']<br />";
}
echo "</td></tr></table>";
I think what you are looking for is referred to a 'concation of subquery'.
Check http://forums.mysql.com/read.php?20,157425,157796#msg-157796 and http://mysql.bigresource.com/SELECT-CONCAT-Subquery-S5cIpzqO.html
I have 2 tables. One (artWork) with all the data I want to pull from, including 2 cols of id's. The other (sharedWork) has the same 2 id cols that are also in the first -- but none of the essential data I want to echo out. Objective: use the id's in both table to filter out row in the first (artWork). See below in the code what I tried that didn't work
I also tried to figure out an inner join that would accomplish the same. No luck there either. Wondering which would be the best approach and how to do it.
thanks
Allen
//////// Get id's first ///////////
$QUERY0="SELECT * FROM artWork WHERE user_id = '$user_id' ";
$res0 = mysql_query($QUERY0);
$num0 = mysql_num_rows($res0);
if($num0>0){
while($row = mysql_fetch_array($res0)){
$art_id0 = $row['art_id'];
}
}
$QUERY1="SELECT * FROM shareWork WHERE user_id = '$user_id' ";
$res1 = mysql_query($QUERY1);
$num1 = mysql_num_rows($res1);
if($num1>0){
while($row = mysql_fetch_array($res1)){
$art_id = $row['art_id'];
}
}
$art_id2 = array_merge($art_id0, $art_id1);
foreach ($art_id2 as $art_id3){
$QUERY="SELECT * FROM artWork WHERE art_id = '$art_id3' ";
// echo "id..".$art_id0;
$res = mysql_query($QUERY);
$num = mysql_num_rows($res);
if($num>0){
while($row = mysql_fetch_array($res)){
$art_title = $row['art_title'];
$art_id = $row['art_id'];
etc................and so on
.........to....
</tr>";
}
}
}
Don't query your database inside a loop unless you absolutely have to.
Everytime you query the database, you're using disk I/O to read through the database and return your record. Disk I/O is the slowest read on a computer, and will be a massive bottleneck for your application.
If you run larger queries upfront, or at least outside of a loop, you will hit your disk less often, improving performance. Your results from larger queries will be held in memory, which is considerably faster than reading from disk.
Now, with that warning out of the way, let's address your actual problem:
It seems you're trying to grab records from artWork where the user is the primary artist, or the user was one of several artists to work on a group project. artWork seems to hold the id of the primary artist on the project whereas shareWork is probably some sort of many-to-many lookup table which associates user ids with all art projects they were a part of.
The first thing I should ask is whether or not you even need the first query to artWork or if the primary artist should have a record for that art_id in shareWork anyway, for having worked on the project at all.
If you don't need the first lookup, then the query becomes very easy: just grab all of the users art_ids from shareWork table and use that to lookup the his or her records in the main artWork table:
SELECT artWork.*
FROM artWork
WHERE art_id IN
(SELECT art_id
FROM shareWork
WHERE user_id = $user)
If you do need to look in both tables, then you just add a check in the query above to also check for that user in the artWork table:
SELECT artWork.*
FROM artWork
WHERE
user_id = $user
OR art_id IN
(SELECT art_id
FROM shareWork
WHERE user_id = $user)
This will get you all artWork records in a single query, rather than.. well, a lot of queries, and you can do your mysql_fetch_array loop over the results of that one query and be done with it.