PHP：按字符数分组计算数量

Question

I have a table ,, as follows:

I want to generate count (count) of each number of characters from mac_addr .. example from the table:

• 15 characters = 5
• 19 characters = 2
• 24 characters = 3

but i want to use one query .. I use now to count each with a different query (not in a single query). example:

$query1 = mysqli_query($conn,"SELECT COUNT(*) AS 'jumlah' FROM orders WHERE ((LENGTH(mac_addr)=15))");
$cek1 = mysqli_fetch_assoc($query1);
$kar1 = $cek1['jumlah'];

$query2 = mysqli_query($conn,"SELECT COUNT(*) AS 'jumlah' FROM orders WHERE ((LENGTH(mac_addr)>15) AND (LENGTH(mac_addr)<24))");
$cek2 = mysqli_fetch_assoc($query2);
$kar2 = $cek2['jumlah'];

$query3 = mysqli_query($conn,"SELECT COUNT(*) AS 'jumlah' FROM orders WHERE ((LENGTH(mac_addr)>19))");
$cek3 = mysqli_fetch_assoc($query3);
$kar3 = $cek3['jumlah'];

echo '15 karakter ='.$kar1;
echo '<br>';
echo '19 karakter ='.$kar2;
echo '<br>';
echo '24 karakter ='.$kar3;
echo '<br>';

well how if made in a single query so as not to eat too much coding / row?

Answer 1

您可以使用group by

SELECT LENGTH(mac_addr) as characters , count(*) AS jumlah FROM orders group by LENGTH(mac_addr)

Answer 2

To be honest, I think you should do this if you want to replace your current method...

SELECT LENGTH(mac_addr), count(mac_addr) FROM orders GROUP BY LENGTH(mac_addr) WHERE LENGTH(mac_addr) > 14

Then take the result and analyze the 15 and up lengths to find exact counts for each grouping.

This could also be done with

SELECT mac_addr FROM orders WHERE LENGTH(mac_addr) > 14

And then analyze it - if first query has any issues.