针对一个PHP变量的多个MYSQL查询

Question

I've broken down individual SQL queries for the information I want from my SQL table but I'm confused on how I can combine all statements agianst one variable. This variable is being used in PHP to display my data.

Here is the SQL queries I'm wanting to run.

SELECT * FROM weather ORDER BY stamp DESC LIMIT 1 

SELECT SUM(rainfall) FROM weather WHERE stamp >= CURDATE()) AS total_rainfall

SELECT MAX(maxwind) FROM weather WHERE stamp >= CURDATE()) AS max_windspeed

SELECT MAX(temperature) FROM weather WHERE stamp >= CURDATE()) AS max_temperature

SELECT MIN(temperature) FROM weather WHERE stamp >= CURDATE()) AS min_temperature

Here is my current query which gives me everything I want except the max windspeed, max temperature, and minimum temperature for the last 24 hours.

 SELECT *, (SELECT SUM(rainfall) FROM weather WHERE stamp >= CURDATE()) AS total_rainfall FROM weather ORDER BY stamp DESC LIMIT 1

Basically, I'm just wanting to add the maximum temperature, minimum temperature and maximum windspeed that occured within the current date.

MySQL data table example

Here is the way I'm trying to display the data using PHP.

<?php

$url1=$_SERVER['REQUEST_URI'];

header("Refresh: 60; URL=$url1");

$connectinfo = mysql_connect("***", "***", "***")
or die(mysql_error());

mysql_select_db("raspberrydb001", $connectinfo);

$sql = "SELECT *, (SELECT SUM(rainfall) FROM weatherdata WHERE stamp >= CURDATE()) AS total_rainfall FROM weatherdata ORDER BY stamp DESC LIMIT 1; ";


$result = mysql_query($sql, $connectinfo);

while($row = mysql_fetch_array($result)) {

$windspeed = $row['windspeed'];
$maxwind = $row['maxwind'];
$temperature = $row['temperature'];
$humidity = $row['humidity'];
$rainfall = $row['rainfall'];
$stamp = $row['stamp'];
$d=mktime();
$total_rainfall = $row['total_rainfall'];

echo "<div style='text-align:center'><h5>Temperature:  " . $temperature . "(F)" . "<br>" . "Rainfall: " . $total_rainfall . "(in)" . "<br>" . "Wind: " . $windspeed . "(MPH)" . "<br>" .  "Humidity: " . $humidity . "(%)" . "<br>" .  "</h5></div>";
echo "<div style='text-align:right'><h6>Updated at: " . $stamp . "</h6></div>";
echo "<br>";

}

?>

Thanks

Answer 1

I would propose to split it up into two queries.

First, to collect all your data:

SELECT * FROM weather ORDER BY stamp DESC LIMIT 1 

Second, to collect the min/max data:

SELECT
    SUM(rainfall) AS total_rainfall, 
    MAX(maxwind) AS max_windspeed, 
    MAX(temperature) AS max_temperature, 
    MIN(temperature)  AS min_temperature 
FROM 
    weather
WHERE stamp >= CURDATE())
LIMIT 1