Get the minimum and maximum number in PHP from DB - php

Question

I'm making a PHP code for showing data of my weather station.
I have a DB in MySQL with 5 columns.
This is my actual code:
<?php
$conexion=mysqli_connect('localhost','dbone','root','dbdata');
?>
<?php
$sql="SELECT * from Sensor ORDER BY id DESC LIMIT 1";
$result=mysqli_query($conexion,$sql);
date_default_timezone_set("Europe/Warsaw");
$calpres=57;
$caltemp=0;
$calhumi=0;
while($mostrar=mysqli_fetch_array($result)){
?>
<?php
?>
|esta=c00m000e00|data=<?php echo date("d-m-Y H:i:s"); ?>|temp=<?php echo $mostrar['value1'] - $caltemp ?>|hum=<?php echo $mostrar['value2'] ?>|pres=<?php echo $mostrar['value3'] + $calpres ?>
<?php
}
?>
The actual result is:
|esta=c00m000e00|data=24-01-2021 19:42:10|temp=10.71|hum=58.20|pres=1016.12
Value1 is the column that includes the temperature. I would like to show the maximum and minimum temperature, but I don't know how to do it.
Thank you very much!

Answer 1

You could use SQL MAX() and MIN() functions.
Something like SELECT MAX(value1) FROM Sensor

Answer 2

Either run 2 queries (one for min and one for max) like this:
(if your column name is temp)
SELECT * from Sensor ORDER BY temp DESC LIMIT 1
SELECT * from Sensor ORDER BY temp ASC LIMIT 1
and the take the first and only rows from them.
A little bit cleaner way is to take all the data you need, ordered by temp, (no LIMIT at the end)
SELECT * from Sensor ORDER BY temp DESC
fetch it in an array, and get the first tempArray[0] and the last tempArray[count(tempArray)-1] - values, they will containt min and max rows.
$result = mysql_query("SELECT * from Sensor ORDER BY temp DESC");
$sensorArray = []
while( $row = mysql_fetch_assoc( $result)){
$sensorArray[] = $row;
}
$max = $sensorArray[0];
$min = $sensorArray[count($sensorArray)-1];