php操作mysql（数据库常规操作）

<code>$servername = "localhost";
$username = "username";
$password = "password";
$dbname = "dbname";
<p>// 建立连接
$conn = new mysqli($servername, $username, $password, $dbname);</code>

<code>// 准备查询语句
$sql = "SELECT * FROM table_name";</p><p>// 执行查询
$result = $conn->query($sql);</p><p>// 处理结果
if ($result->num_rows > 0) {
// 输出每一行数据
while($row = $result->fetch_assoc()) {
echo "id: " . $row["id"] . " - Name: " . $row["name"] . "<br></br>";
}
} else {
echo "没有结果";
}</code>

<code>// 准备插入语句
$sql = "INSERT INTO table_name (name, age) VALUES ('John', 30)";</p><p>// 执行插入操作
if ($conn->query($sql) === TRUE) {
echo "新记录已成功创建";
} else {
echo "错误: " . $conn->error;
}</code>

<code>// 准备更新语句
$sql = "UPDATE table_name SET name='Mary' WHERE id=1";</p><p>// 执行更新操作
if ($conn->query($sql) === TRUE) {
echo "记录已成功更新";
} else {
echo "错误: " . $conn->error;
}</code>

<code>// 准备删除语句
$sql = "DELETE FROM table_name WHERE id=1";</p><p>// 执行删除操作
if ($conn->query($sql) === TRUE) {
echo "记录已成功删除";
} else {
echo "错误: " . $conn->error;
}</code>

<code>// 关闭数据库连接
$conn->close();</code>