php sql更新仅在字段中填写

（这是所有的基础课程或学校） 我制作了一个表单，您可以在其中更新您的帐户信息，当您点击提交按钮时，它将出现在这个php代码中。如果一个字段没有填写，它就不需要更新，我尝试了“wherefieldnotnull”，但它似乎不起作用，它给出了一个空记录

（对不起，变量都是荷兰语）

---

当然，我需要说明“字段”的其余部分不是空的，但例如，我只使用“naam”。。但是它不起作用：/

如果您将这部分逻辑远离数据库，可能是最简单的

<?php
$con = mysql_connect("localhost","root","root");
if (!$con)
{
    die('Could not connect: ' . mysql_error());
}

if ( !mysql_select_db("opdracht3", $con) ) {
    die('Could not connect: ' . mysql_error());
}

// contains strings/parameters/identifiers ready-for-use with mysql  
$sql_params = array(
    'fields' => array('naam', 'adres', 'postcode', 'gemeente', 'gezinsleden', 'huidigemeterstand', 'vorigemeterstand', 'provincie'),
    'klantnummer' => mysql_real_escape_string($_COOKIE['klantnummer']),
    'updates' => array()
);

// the names of the POST-fields are the same as the column identifiers of the database table
// go through each identifier
foreach( $sql_params['fields'] as $f ) {
    // put in here the conditions for "an empty field, e.g.
    // if there is such POST-field and its value is one or more "usable" characters long
    if ( isset($_POST[$f]) && strlen(trim($_POST[$f])) > 0 ) {
        // create a new `x`=`y` "line" as in UPDATE ... SET `x`='y'
        // and append it to the array $sql_params['updates']
        $sql_params['updates'][] = sprintf("`%s`='%s'", $f, mysql_real_escape_string($_POST[$f]));
    }
}

// the "lines" in $sql_params['updates'] need to be concatenated with , between them
// join(', ', $sql_params['updates']) does that
// insert that string and the parameter klantnummer into the query string
$query = sprintf(
    "
        UPDATE
            waterstand
        SET
            %s
        WHERE
            klantnummer = '%s'
    ",
    join(', ', $sql_params['updates']),
    $sql_params['klantnummer']
);

---

首先停止使用
mysql_uu>函数
，它们已被弃用。开始使用PDO，如果数据库字段中的默认值设置为NULL会更好、更安全吗？如果设置为“”或类似值，则IS NULL check将不会返回true。@本·凯里：这是我们在学校学习的方式，但我会检查出来，谢谢@Maccath:Thx，我会看看这是否是问题所在。WHERE子句“引用”了更新之前的记录，也就是说，在可能的更新发生之前，您的非空条件测试记录是否有空值。哇，非常感谢@VolkerK，但我认为代码对我来说不可读：D，我们正在学习基础知识，我不理解这段代码，很抱歉：/。我查看了您提供给我的筛选器页面，我想使用filter\u has\u var函数，对吗？很抱歉，该链接可能会误导您，因为它在修改查询字符串方面帮不了您多少忙。添加到示例脚本的注释。
<?php
$con = mysql_connect("localhost","root","root");
if (!$con)
{
    die('Could not connect: ' . mysql_error());
}

if ( !mysql_select_db("opdracht3", $con) ) {
    die('Could not connect: ' . mysql_error());
}

// contains strings/parameters/identifiers ready-for-use with mysql  
$sql_params = array(
    'fields' => array('naam', 'adres', 'postcode', 'gemeente', 'gezinsleden', 'huidigemeterstand', 'vorigemeterstand', 'provincie'),
    'klantnummer' => mysql_real_escape_string($_COOKIE['klantnummer']),
    'updates' => array()
);

// the names of the POST-fields are the same as the column identifiers of the database table
// go through each identifier
foreach( $sql_params['fields'] as $f ) {
    // put in here the conditions for "an empty field, e.g.
    // if there is such POST-field and its value is one or more "usable" characters long
    if ( isset($_POST[$f]) && strlen(trim($_POST[$f])) > 0 ) {
        // create a new `x`=`y` "line" as in UPDATE ... SET `x`='y'
        // and append it to the array $sql_params['updates']
        $sql_params['updates'][] = sprintf("`%s`='%s'", $f, mysql_real_escape_string($_POST[$f]));
    }
}

// the "lines" in $sql_params['updates'] need to be concatenated with , between them
// join(', ', $sql_params['updates']) does that
// insert that string and the parameter klantnummer into the query string
$query = sprintf(
    "
        UPDATE
            waterstand
        SET
            %s
        WHERE
            klantnummer = '%s'
    ",
    join(', ', $sql_params['updates']),
    $sql_params['klantnummer']
);