PHP 和 MySQL - 处理 NULL 示例
您可以使用if...else条件来准备基于NULL值的查询。
以下示例从外部获取tutorial_count，然后将其与表中的可用值进行比较。
示例
将以下示例复制并粘贴为 mysql_example.php −
<html>
<head>
<title>Handling NULL</title>
</head>
<body>
<?php
$dbhost = 'localhost';
$dbuser = 'root';
$dbpass = 'root@123';
$dbname = 'TUTORIALS';
$mysqli = new mysqli($dbhost, $dbuser, $dbpass, $dbname);
$tutorial_count = null;
if($mysqli->connect_errno ) {
printf("Connect failed: %s<br />", $mysqli->connect_error);
exit();
}
printf('Connected successfully.<br />');
if( isset($tutorial_count )) {
$sql = 'SELECT tutorial_author, tutorial_count
FROM tcount_tbl
WHERE tutorial_count = ' + $tutorial_count;
} else {
$sql = 'SELECT tutorial_author, tutorial_count
FROM tcount_tbl
WHERE tutorial_count IS NULL';
}
$result = $mysqli->query($sql);
if ($result->num_rows > 0) {
while($row = $result->fetch_assoc()) {
printf("Author: %s, Count: %d <br />",
$row["tutorial_author"],
$row["tutorial_count"]);
}
} else {
printf('No record found.<br />');
}
$mysqli->close();
?>
</body>
</html>
输出
访问部署在 apache Web 服务器上的 mysql_example.php 并验证输出。
Connected successfully. No record found.
