I want to select the maximum value of a column of my table. I'm using PHP and MySQL. This is what I have so far:
$max = "SELECT MAX(Id) FROM trialtabel2";
$max1 = mysqli_query($dblink, $max);
echo= $max1;
My debugger is just saying that it is a query returning a 0 boolean value (false). I cannot find a specific answer anywhere on the internet.
You need to fetch the data from the mysqli_result object that was returned to you when you executed your query using mysqli_query.
$max = "SELECT MAX(Id) as id FROM trialtabel2";
$max1 = mysqli_query($dblink, $max);
$row = mysqli_fetch_assoc($max1); // this was missing
$id=$row['id'];
echo $id;
Note: I removed the loop because with MAX query without any grouping you will get only 1 row returned. If you had multiple rows in result set you would need to loop through all of them
two ways
first is as people described
$max = "SELECT MAX(Id) as max_id FROM trialtabel2";
$max1 = mysqli_query($dblink, $max);
$row = mysqli_fetch_assoc($max1);
$max_id=$row['max_id'];
echo $max_id;
second is ordering and limiting
$max_id = 0;
$max = "SELECT id FROM trialtabel2 order by id desc limit 0,1";
$max1 = mysqli_query($dblink, $max);
while($row = mysqli_fetch_assoc($max1)){
$max_id=$row['id'];
}
echo $max_id;
In Your code you missing the fetch statement. you need to fetch from the resultset. see above what you are missing.
Try using this..,
$max = "SELECT MAX(Id) as maxId FROM trialtabel2";
$max1 = mysqli_query($dblink, $max);
$row = mysqli_fetch_assoc($max1);
echo $row['maxId'];
Hope this helps..
$max = "SELECT Id FROM trialtabel2 order by id desc limit 1";
$max1 = mysqli_query($dblink, $max);
$result = mysqli_fetch_assoc($max1);
pre($result);
Related
I want to get the sum total of the table columns in my database.
I've tried using the following code but have not been successful.
$link=mysqli_connect(DB_SERVER,DB_USERNAME,DB_PASSWORD,DB_NAME);
$result = mysqli_query($link,'SELECT SUM(value) AS value_sum FROM User_Table');
$row = mysqli_fetch_assoc($result);
$sum = $row['value_sum'];
echo $sum;
Thank you very much!!
I hope you try to find total number of record of a table of User_Table
$link=mysqli_connect(DB_SERVER,DB_USERNAME,DB_PASSWORD,DB_NAME);
$result = mysqli_query($link,'SELECT SUM(your_column_name) AS value_sum FROM User_Table');
//or like the query for return last row that indicate total number of record
// id auto increment
$result = mysqli_query($link,'SELECT * FROM User_Table ORDER BY id DESC LIMIT 1;');
$row = mysqli_fetch_assoc($result);
$sum = $row['id'];
echo $sum;
// or using count
$result = mysqli_query($link,'SELECT COUNT(*) total_row FROM User_Table;');
$row = mysqli_fetch_assoc($result);
$sum = $row['total_row '];
echo $sum;
As of my understanding you need count the number of columns your database have. If I am not wrong, you may please use the query below
select * from information_schema.columns
where table_schema = '<YOUR DATABASE NAME>'
order by table_name,ordinal_position
Hope this helps. Thanks
I have a table and i want to echo the 2 last rows of my tabel, I used the below code but just the last one showed, what is the problem.
$result1 =(mysql_fetch_array(mysql_query("SELECT * FROM $table ORDER BY id DESC LIMIT 2")));
Print $result1['time'];
mysql_fetch_array = 1 fetch.
do it again for fetching 2nd result.
Also, use mysqli eh.
You're doing mysql_fetch_array only one time, so it gets the first element. If you want to get all the elements, then do it again, or use a loop.
Something like:
$query = "SELECT * FROM $table ORDER BY id DESC LIMIT 2";
while($row = mysql_fetch_array(mysql_query($query) )
{
echo $row['time'].'<br>';
}
For 2 Or more rows you need to loop it
$sql = mysql_query("SELECT * FROM $table ORDER BY id DESC LIMIT 2")
while($row=mysql_fetch_array($sql))
{
echo $row['time']."<br>";
}
$query = mysqli_query("SELECT * FROM $table ORDER BY id DESC LIMIT 2");
while ($result = mysqli_fetch_array($query)) {
echo $result['time'];
}
Gives out every return of your database (2 in this case). You should use mysqli_-functions.
Maybe you should try like this, since mysql_fetch_array returns only one row
while ($row = mysql_fetch_array($yourQuery)) {
echo $row["yourAlias"];
}
Further details here : http://fr2.php.net/manual/en/function.mysql-fetch-array.php
My solution:
$limit = 2;
$sql = "SELECT * FROM $table ORDER BY id DESC LIMIT $limit";
$result = mysql_query($sql);
$array = array(); $i = 0;
while($row = mysqli_fetch_array($result))
{
$array[$i] = $row;
$i++;
}
var_dump($array[0]);
var_dump($array[1]);
I'm trying to get a random value from an array that is populated with data from the database. I'm selecting some products from the DB and display them on the front page, but i need to display different (random) producs everytime the page is reloaded.
$row = mysql_query("SELECT * FROM anunt WHERE lichidareStoc = 0 ORDER BY anuntID DESC") or die(mysql_error());
$row2 = mysql_fetch_assoc($row);
So, i think that $row2 is now an array, and has all the infos that i selected previously from the database. How do i select a random 'row' from that array now?
Thanks
You are looking for array_rand, see: http://php.net/manual/en/function.array-rand.php
Example:
$rand_key = array_rand($row2);
echo $row2[$rand_key]; // your random
You could also directly select a random row from your DB:
SELECT *
FROM anunt
WHERE lichidareStoc = 0
ORDER BY rand()
LIMIT 1
But be aware, this will reduce your performance, especially on bigger tables.
Side Note: mysql_* function are deprecated, use mysqli_* instead.
If you want to select a random entry, you could do something like this:
$myRows=array();
$row = mysql_query("SELECT * FROM anunt WHERE lichidareStoc = 0 ORDER BY anuntID DESC") or die(mysql_error());
while($row2 = mysql_fetch_assoc($row))
$myRows[]=$row2;
$randomEntry=$myRows[array_rand($myRows)];
If you wanted a random field of that entry though, you should use array_rand like Bernhard Poiss pointed out.
$row = mysql_query("SELECT * FROM anunt WHERE lichidareStoc = 0 ORDER BY anuntID DESC") or die(mysql_error());
$row2 = mysql_fetch_assoc($row);
$randomField=$row2[array_rand($row2)];
You will first want to populate an array of your results
$row = mysql_query("SELECT * FROM anunt WHERE lichidareStoc = 0 ORDER BY anuntID DESC") or die(mysql_error());
$rows = array();
while($rec = mysql_fetch_assoc($row)){
$rows[] = $rec;
}
Then you can select a random item using array_rand
$random = $rows[array_rand($rows)];
I recently combined 2 queries into 1 (to optimize performance)...1 query for checking the count, and the other for the results, the count is to ensure their is actual results their before proceeding with the loop.
Heres the PHP code:
<?php
$query = 'SELECT id, title, COUNT(id) FROM submissions ORDER BY sub_time DESC LIMIT 50';
$result = mysql_query($query);
$count = mysql_result($result, 0, 2);
mysql_data_seek($result, 0); //mysql_result resets the internal pointer...
if ($count > 0) {
$i = 0;
while ($output = mysql_fetch_assoc($result)) {
++$i;
//etc..
}
}
?>
The problem is it now returns 1 result? - when theirs actually 2 results inside (as I've checked via PHPMyAdmin aswell as running the following code - see below), I've narrowed down the problem, its because the COUNT(id) has been combined with the intial results query; that its behaving like this.
Because if I do the following:
<?php
$query = 'SELECT id, title FROM submissions ORDER BY sub_time DESC LIMIT 50';
$result = mysql_query($query);
$i = 0;
while ($output = mysql_fetch_assoc($result)) {
++$i;
//etc..
}
?>
It returns 2 results...
So my question is how do i resolve this but achieve what I'm after?
I would recommend that you remove the COUNT(id) and use the mysql_num_rows() function to check how many rows were returned before trying to loop through them.
Your code could then look like this:
<?php
$query = 'SELECT id, title FROM submissions ORDER BY sub_time DESC LIMIT 50';
$result = mysql_query($query);
$count = mysql_num_rows($result);
if ($count > 0) {
$i = 0;
while ($output = mysql_fetch_assoc($result)) {
++$i;
//etc..
}
}
COUNT is an aggregate function that typically is used with the GROUP BY clause. I don't believe it is meaningful in the query as you used it.
Suppose I have a while loop like:
$sql = mysql_query("SELECT * FROM tablename");
while($row = mysql_fetch_array($sql)){
$id = $row["id"];
$sql_2 = mysql_query("SELECT * FROM secondtable WHERE id != $id ");
while($ro = mysql_fetch_array($sql_2)){
$id2 = $ro["id2"];
echo $id2;
}
}
then if first query return 5 results i.e 1-5 and second query returns 3 results than if i want to echo out second query it gives me like this..........
111112222233333
than how can i fix to 123 so that the second while loop should execute according to number of times allowed by me........!! how can i do that.........!!
I'm not sure I 100% understand your question - it's a little unclear.
It's possible you could solve this in the query with a GROUP BY clause
$sql_2 = mysql_query("SELECT id FROM secondtable WHERE id != $id GROUP BY id");
But that would only work if you need just secondtable.id and not any of the other columns.
When you say "number of time allowed by me" do you mean some sort of arbitrary value? If so, then you need to use a different loop mechanism, such as Greg B's solution.
Do you want to explicitly limit the number of iterations of the inner loop?
Have you considered using a for loop?
$sql = mysql_query("SELECT * FROM tablename");
while($row = mysql_fetch_array($sql)){
$id = $row["id"];
$sql_2 = mysql_query("SELECT * FROM secondtable WHERE id != $id ");
for($i=0; $i<3; $i++){
$ro = mysql_fetch_array($sql_2);
$id2 = $ro["id2"];
echo $id2;
}
}
Your first while loop is iterating over all 5 results, one at a time.
Your second while loop is iterating over each of the 5 results, producing it's own set of results (i.e. 3 results for each of the 5 iterations, totaling 15 results).
I believe what you are trying to do is exclude all IDs found in your first loop from your second query. You could do that as follows:
$sql = mysql_query("SELECT * FROM tablename");
$exclude = array();
while($row = mysql_fetch_array($sql)) {
array_push($exclude, $row['id']);
}
// simplify query if no results found
$where = '';
if (!empty($exclude)) {
$where = sprintf(' WHERE id NOT IN (%s)', implode(',', $exclude));
}
$sql = sprintf('SELECT * FROM secondtable%s', $where);
while($row = mysql_fetch_array($sql_2)) {
$id2 = $row["id2"];
echo $id2;
}
$sql = mysql_query("SELECT * FROM tablename");
$tmp = array();
while($row = mysql_fetch_array($sql)){
$id = $row["id"];
if(!in_array($id, $tmp)) {
$sql_2 = mysql_query("SELECT * FROM secondtable WHERE id != $id ");
while($ro = mysql_fetch_array($sql_2)){
$id2 = $ro["id2"];
echo $id2;
}
$tmp[] = $id;
}
}
Saving all queried $id's in an array to check on the next iteration if it has already been queried. I also think that GROUPing the first query result would be a better way.
I agree with Leonardo Herrera that it's really not clear what you're trying to ask here. It would help if you could rewrite your question. It sounds a bit like you're trying to query one table and not include id's found in another table. You might try something like:
SELECT * FROM secondtable t2
WHERE NOT EXISTS (SELECT 1 FROM tablename t1 WHERE t1.id = t2.id);