PHP MySQL UPDATE only one Cell, instead of whole row - php

Question

So i have a table with a row, click on 'bearbeiten', i get to a formula where i can fill in the changed name or whatever, and then everything changes instead of only the fields i wrote something in and the rest stays.
So if i would only change name and click on save, every other field in the table goes blank.
I tried it with WHERE already, and read that POST is a good method but i think i can change it with making a few changes in the $sql statement, just don't know what.
<?php
//if(isset($...)
if($_GET['aktion'] == "speichern")
{
$ID = $_GET['ID'];
$Anrede = $_GET['Anrede'];
$Nachname = $_GET['Nachname'];
$Vorname = $_GET['Vorname'];
$Geburtsdatum = $_GET['Geburtsdatum'];
$Telefonnummer = $_GET['Telefonnummer'];
$Email = $_GET['Email'];
$sql = "UPDATE Adressbuch SET Anrede = '$Anrede', Nachname = '$Nachname',Vorname = '$Vorname', Geburtsdatum = '$Geburtsdatum', Telefonnummer = '$Telefonnummer', Email = '$Email' ORDER BY ID DESC LIMIT 1";
echo 'Zurueck zum Adressbuch<br>';
require_once ('konfiguration.php');
$db_erg = mysqli_query($db_con, $sql)
or die("Anfrage fehlgeschlagen: " . mysqli_error($db_con));
exit;
}

Answer 1

How about:
Just update the column, if you variable is not blank, else update it with the same value as the record already has.
UPDATE Adressbuch
SET Anrede = CASE WHEN '$Anrede' != '' THEN '$Anrede' ELSE Anrede END
,Nachname = CASE WHEN '$Nachname' != '' THEN '$Nachname' ELSE Nachname END
,Vorname = CASE WHEN '$Vorname' != '' THEN '$Vorname' ELSE Vorname END
,Geburtsdatum = CASE WHEN '$Geburtsdatum' != '' THEN '$Geburtsdatum' ELSE Geburtsdatum END
,Telefonnummer = CASE WHEN '$Telefonnummer' != '' THEN '$Telefonnummer' ELSE Telefonnummer END
,Email = CASE WHEN '$Email' != '' THEN '$Email' ELSE Email END
ORDER BY ID DESC LIMIT 1

Answer 2

Use as and see if it works. Thanks.
<?php
require_once ('konfiguration.php');
//if(isset($...)
if($_GET['aktion'] == "speichern")
{
$ID = $_GET['ID'];
$Anrede = $_GET['Anrede'];
$Nachname = $_GET['Nachname'];
$Vorname = $_GET['Vorname'];
$Geburtsdatum = $_GET['Geburtsdatum'];
$Telefonnummer = $_GET['Telefonnummer'];
$Email = $_GET['Email'];
//use where in your query to update the particular row
//in below query id = your column in database table
$sql = "UPDATE Adressbuch SET Anrede = '$Anrede', Nachname = '$Nachname',Vorname = '$Vorname', Geburtsdatum = '$Geburtsdatum', Telefonnummer = '$Telefonnummer', Email = '$Email' WHERE id='$ID'";
$db_erg = mysqli_query($db_con, $sql) or die("Anfrage fehlgeschlagen: " . mysqli_error($db_con));
echo 'Zurueck zum Adressbuch<br>';
exit;
}
?>
Use POST method instead of GET.