选择按天分组的列值总和

Question

I have a table with columns datetime, order value, and number of pieces for each order issued. Datetime is in standard datetime mysql format.

To get the total sum of orders, I have a query like this:

$sqlsum = "SELECT SUM(order_value) FROM orders";
if (mysqli_query($conn, $sqlsum)) {
    $resultsum = mysqli_query($conn, $sqlsum);
    while($row = mysqli_fetch_assoc($resultsum)) {
        $total_sales = $row['SUM(order_value)'];

        // and here I use the value in a simple report
    }
}

To get a report of all single orders, usually I'd do like this:

<?php

$sql = "SELECT * FROM orders";
$result = mysqli_query($conn, $sql);
if (mysqli_num_rows($result) > 0) {
    while($row = mysqli_fetch_assoc($result)) {
        $order_time = $row["datetime"];
        $order_value = $row["order_value"];
        $pieces_number = $row["pieces"];

        // and here I use the results in a detailed report
    }
}
?>

Now I have to make two different reports, one for each day and one for each month, and each one has to show:
- count of orders
- sum of order values
- sum of number of pieces
How should be the query to get the count of orders per day and the sum of values and pieces per day?

Googled the site for similar issues, but didn't find a post with a clear solution for my needs.

Answer 1

In the 1st case you need to group by day using the DATE() function:

SELECT 
  DATE(datetime) day, 
  COUNT(*) orderscounter,
  SUM(order_value) valuesum,
  SUM(pieces) piecessum
FROM orders
GROUP BY day

In the 2nd case you need to group by year/month using the YEAR() and MONTH() functions:

SELECT 
  YEAR(datetime) year,
  MONTH(datetime) month, 
  COUNT(*) orderscounter,
  SUM(order_value) valuesum,
  SUM(pieces) piecessum
FROM orders
GROUP BY year, month