I can not find a proper answer to this question. I have a very simple code for making a query in mysql to select the row with the maximum value in a determined column (called popularity) from a table (called comments). Every row has a column named comment_id
here is the code:
$connect_error = 'Sorry, try again, there was a connection error';
$con = mysqli_connect('localhost','user_name','password') or die($connect_error);
mysqli_select_db($con, 'database') or die($connect_error);
$result = mysqli_query($con, "SELECT MAX(`popularity`) FROM `comments`");
while ($row = mysqli_fetch_assoc($result)) {
$most_popular = $row['comment_id'];
}
echo "most popular is: $most_popular";
mysqli_free_result($result);
mysqli_close($con);
the screen does not show a proper result. Can someone give me an advice in this regard?
Thank you
You are looking to display the comment_id field, but you don't have that in your SELECT query. You are only selecting the max popularity value, and nothing else.
Try this for your query:
SELECT comment_id FROM comments ORDER BY popularity DESC LIMIT 1
This is sorting your comments by popularity, and then just picking the top one.
Of course you can easily change that to select more columns or even a SELECT * if you want to be able to display other values in this record.
To select the row with max 'popularity' column use this query;
$result = mysqli_query($con, "SELECT * FROM `comments` ORDER BY `popularity` DESC LIMIT 1");
In case you want all sorted by popularity remove the LIMIT 1...
You need
SELECT MAX(`popularity`) AS comment_id FROM `comments`
This will give the column the correct name for the associated array.
You are trying to read the result from a column named comment_id when the result from your query will be named MAX(popularity)
Run this query in mysql "SELECT MAX(popularity) FROM comments" first.The output of this gives you the index to use with $row[index] ie first row which in this case the index will be popularity else just change $row[content_id] to $row[popularity]
Related
So I've been stuck on this for a while and I can't find anything on google for this specific thing.
I have this small snippet of code
$link = mysqli_connect("localhost", 'username','password',"database");
$sql = "SELECT * FROM `uploads` ORDER BY id DESC LIMIT 0, 1";
Which should select the latest table by order of id's right?
Well what I want to do is return this id. So if I have 5 items/rows I want to grab the latest (5 in this case) id of the table, and return it. With the eventual goal of using this returned id in javascript but that's a worry for later, right now I just want it in plaintext where the result should only be the id.
This is probably a duplicate question but I can't for the life of me find what I should google to get there
EDIT:
I guess I should clarify further. I know I'm able to do
$sql = "SELECT ID FROM `uploads` ORDER BY id DESC LIMIT 0, 1";
but whenever I try to actually retrieve it/print it its returned as a string instead of the ID.
EDIT 2: I, thanks to some comments, have managed to figure it out. Sorry for the badly worded everything, I'm new to this and as I said don't know how to word it.
SOLUTION:
After just throwing away the $sql thing I added:
$result = mysqli_query($link,"SELECT * FROM `uploads`");
Then I simply did
echo mysqli_num_rows($result);
To echo out the number of rows/what I called the "ID".
Sorry for all the confusion, thanks to those that tried to help. To the others there's no need to be rude.
If I understood your question correctly, you want to get the ID field only, so you have two options:
Option 1 (Recommended)
Given your code
$sql = "SELECT * FROM `uploads` ORDER BY id DESC LIMIT 0, 1";
Change it to:
$sql = "SELECT ID FROM `uploads` ORDER BY id DESC LIMIT 0, 1";
This way, your getting just that ID field you're after. Nothing else is returned from each row.
Option 2
Keep your sql query as it is, and get the ID field from each row in your results (it's an array, so you can retrieve only one field by using its index or name).
Of course, I assume there's an ID field in your table!
Just select the ID.
SELECT id
FROM uploads
ORDER BY id DESC
LIMIT 1;
Simply select what you want.
$sql = "SELECT id FROM `uploads` ORDER BY id DESC LIMIT 0, 1";
The * means you want to select every column there is. However, SQL gives you the possibility to select the specific columns you want. You could also do something like
$sql = "SELECT id, name, title, somethingelse FROM `uploads` ORDER BY id DESC LIMIT 0, 1";
and you'd receive these 4 fields as an array.
i'm trying to find the highest number in my table (named huur) from column Borga but only for the user where the ID2 is equal to the number i have in the variable named $ID2. The highest number should go into the variable $hoogste_borg
this is the code i'm using, but i get invalid syntax error? what am i doing wrong?
<?php
$query="SELECT MAX('Borga') FROM huur ORDER BY ID DESC LIMIT 1 WHERE ID2='$ID2'";
$result=mysql_query($query) or die ("Error: ".mysql_error());
while ($row=mysql_fetch_array($result))
{
$hoogste_borg=$row['Borga'];
}
?>
ORDER BY and LIMIT must go after WHERE clauses. -- http://dev.mysql.com/doc/refman/5.0/en/select.html
SELECT MAX('Borga')
FROM huur
WHERE ID2='$ID2'
ORDER BY ID DESC
LIMIT 1
Try to do this:
$query="SELECT MAX('BORGA') as Borga...";
Cause you want the 'Borga' field, but SQL return MAX('Borga')
If it doesn't work do this:
var_dump($row);
And show us the result :)
I have a table as below,
ID Name Age
----------------------
100 A 10
203 B 20
Now how do i select only row1 using MySQL SELECT command and then I've to increase +1 to it to select row2. In short I'll be using for loop to do certain operations.
Thanks.
Sounds like you've got a mix up. You want to select all the rows you want to iterate through in your for loop with your query, and then iterate through them one by one using php's mysql functions like mysql_fetch_row
You should not try to use tables in a linear fashion like this. Set your criteria, sorting as appropriate, and then to select the next row use your existing criteria and limit it to one row.
SELECT * FROM `table` ORDER BY `ID` LIMIT 1
SELECT * FROM `table` ORDER BY `ID` WHERE ID > 100 LIMIT 1
You'd probably be better off retrieving all rows that you need, then using this. Note the LIMIT is entirely optional.
$query = mysql_query(' SELECT ID, Name, Age FROM table_name WHERE condition LIMIT max_number_you_want '))
while ($row = mysql_fetch_assoc($query)
{
// Do stuff
// $row['ID'], $row['Name'], $row['Age']
}
Lots of small queries to the database will execute much slower than one decent-sized one.
You should get the result into an array (php.net : mysql_fetch_*).
And after you'll can loop on the array "to do certain operations"
Yep, this is a pretty common thing to do in PHP. Like the others who have posted, here is my version (using objects instead of arrays):
$result = mysql_query("SELECT * FROM table_name");
while ($row = mysql_fetch_object($result)) {
// Results are now in the $row variable.
// ex: $row->ID, $row->Name, $row->Age
}
I want to count how many rows I have in a mysql table and display it in html.
For example:
There is: Item 1, Item 2, Item 3, Item 4, Item 5, Item 6
If Item 1 and Item 2 are filled, I want a html code to say - 2 items in row
any ideas?
you can use simple
Select count(*) from table
or If you want not null values
Select count(item) from table
IF its total rows you are after, then as Nishant mentioned above you could do something like this
$query = "SELECT COUNT(*) FROM mytable WHERE myfield='myvalue'";
I am counting all the ids, because it will reduce the time taken to calculate the total instead of '*' and
Thanks to Nico, count(*) and count(column) are not so different considering performance. Here is a comparision
Use a where condition to narrow your total as you require.
If you want to count only rows which are filled (meaning, which are not null), you should add a small WHERE clause, or specify the column of interest in the count() function:
using where
SELECT count(*) FROM mytable WHERE fieldx IS NOT NULL
specifying the field of interest
SELECT count(fieldx) FROM mytable
in this last solution, count() will only take into account not-null fieldx values.
You can get the number of rows of your query using the function mysql_num_rows().
So if you have a SELECT statement (to select which items you want), you just have to call mysql_num_rows() after doing the query. Example from php.net:
$link = mysql_connect("localhost", "mysql_user", "mysql_password");
mysql_select_db("database", $link);
$result = mysql_query("SELECT * FROM table1", $link);
$num_rows = mysql_num_rows($result);
echo "$num_rows Rows\n";
What do you mean by filled? Anyway, if by 'filled' you mean that some specific field has a NOT NULL value you could do something like this:
$sqlConn = new mysqli('host', 'user', 'password', 'database');
$sqlConn->query('SELECT * FROM table WHERE field1 IS NOT NULL AND field2 IS NOT NULL');
echo 'You have ' . $sqlConn->affected_rows . ' rows.';
Hope it helps.
I want to fetch the last result in MySQL database table using PHP. How would I go about doing this?
I have 2 Columns in the Table, MessageID(auto) & Message.
I already know how to connect to the database.
Use mysql_query:
<?php
$result = mysql_query('SELECT t.messageid, t.message
FROM TABLE t
ORDER BY t.messageid DESC
LIMIT 1') or die('Invalid query: ' . mysql_error());
//print values to screen
while ($row = mysql_fetch_assoc($result)) {
echo $row['messageid'];
echo $row['message'];
}
// Free the resources associated with the result set
// This is done automatically at the end of the script
mysql_free_result($result);
?>
The SQL query:
SELECT t.messageid, t.message
FROM TABLE t
ORDER BY t.messageid DESC
LIMIT 1
...uses the ORDER BY to set the values so the highest value is the first row in the resultset. The LIMIT says that of all those rows, only the first is actually returned in the resultset. Because messageid is auto-increment, the highest value is the most recent one...
Records in a relational database do not have an intrinsic "order" so you cannot fetch the "last" record without some kind of ORDER BY clause.
Therefore, in order to fetch the "last" record, simply reverse the ORDER BY clause (change ASC to DESC or vice versa) then select the first result.
If you have an auto-increment field and you just want to find the last value that was inserted, you can use the fact that the auto-increment fields are ever-increasing (therefore the "last" one will be the one with the highest value) and do something like this:
SELECT *
FROM my_table
ORDER BY id_field DESC
LIMIT 1
Of course you can select the last row by sorting DESC in your query. But what if you want to select the first row and then the last. You can run a new query, but you can also use the function mysql_data_seek. check code below:
$result = mysql_query('YOUR QUERY') or die('Invalid query: ' . mysql_error());
$row_first = mysql_fetch_array($result);
mysql_data_seek($result , (mysql_num_rows($result)-1));
$row_last = mysql_fetch_array($result);
Hope this helps
The MySql query would look like this:
select MessageID, Message
from Table
order by MessageID desc
limit 1;
I am too rusty with PHP to give you the right syntax for executing this.
This query works because you have an auto-incrementing identifying field (MessageID). By ordering the results by that field in descending (largest to smallest) order we are effectively returning the records in the table in reverse order. The limit 1 clause simply limits the result set to one record - the last one in the table.
What do you mean by "the last result"? You need to precise a bit more.
Do you mean "the last entry I registered"?
In this case you should use the appropriate method (depending on the extension you are using) mysqli->insert_id OR mysql_insert_id.
If you mean "the latest entry in the table", an SQL query such as Andrew Hare's is just what you need.
Do you mean the last record or do you need the id of the most recently inserted record? For that you would use the PHP mysql_insert_id() function. Or if you are using the myusqli extension use $mysqli->insert_id.
for some reason (which I don't know why), my boss force me to get the data in this way:
$message_arr = array();
while ($row = mysql_fetch_assoc($result)) {
$message_arr['messageid']= $row['messageid'];
$message_arr['message']= $row['message'];
}
return $message_arr;
Of course, you need everything from OMG Ponies's answer I'm just telling you another way to do it =)
I hope this help.
You should use SELECT query. How SELECT works.
SELECT * FROM table - selects everything in a table (id, row 1, row 2,...)
SELECT id FROM table - selects only particular row from table.
If you now know, how to select, you can use additional logic.
SELECT * FROM table ORDER by id DESC LIMIT 1;
selects everything from table table, orders it by id - orders it DESCENDING and limits the query to only one result.
If you would do it like this:
SELECT * FROM table ORDER by id ASC limit 1; - you would get 1 entry into database.
You can order it by any row you want.
Hope it helps.
One thing to remember is that data does not get saved in the insertion order in any MYSQL database. So in order to get the last entered record u will have to have an auto increment field. Since there is an auto increment field in this table we are good to go.
The below script will help to get the last entered record
<?php
$sql = "SELECT * FROM table_name ORDER BY MessageID DESC LIMIT 2";
$result_set = mysql_query($sql);
if($result_set){
while($row = mysql_fetch_array($result_set)) {
echo "Message Id: ".$row['MessageID']."<br>";
echo "Message: ".$row['Message']."<br>";
}
//creating alert
echo "<script type=\"text/javascript\">alert('Data was Retrieved
successfully');</script>";
}
else{
//creating alert
echo "<script type=\"text/javascript\">alert('ERROR! Could Not Retrieve
Data');</script>";
}
?>
The query selects all the records in the table and orders them according to the descending order of the MessageID (as it is the auto increment field) and limits the returned result to only one record. So since the table is ordered according to the descending order of the MessageID only the last entered record will be returned.
NOTE: if you are using a newer version you will have to use mysqli_query($connection_variable,$sql); instead of mysql_query($sql); and mysqli_fetch_array($result_set) instead of mysql_fetch_array($result_set)
$result = mysql_query('select max(id) from your_table ') or die('Invalid query: ' . mysql_error());
while ($row = mysql_fetch_assoc($result)) {
echo $row['id'];
echo $row['message'];
}
//
//
mysql_free_result($result);
simple like that
this code of php works fine
SELECT t.messageid, t.message
FROM TABLE t
ORDER BY t.messageid DESC
LIMIT 1
if you don't have concurrent entries going into some table.b'cause concurrent entries may not go in accordance of their insertion order.
$statement = $PDO->prepare("
SELECT MessageID,
Message
FROM myTable
ORDER BY MessageID DESC
LIMIT 1;
");
$statement->execute();
$result = $statement->fetch(\PDO::FETCH_ASSOC);
echo $result['MessageID']." and ".$result['Message'];