PHP基础回顾之My SQL（七）

连接 MySQL

<?php
$servername = "localhost";
$username = "username";
$password = "password";

// 创建连接
$conn = new mysqli($servername, $username, $password);

// 检测连接
if ($conn->connect_error) {
    die("连接失败: " . $conn->connect_error);
} 
echo "连接成功";
?>

关闭连接

$conn->close(); 

创建 MySQL 数据库
CREATE DATABASE 语句用于在 MySQL 中创建数据库。在下面的实例中，创建了一个名为 “myDB” 的数据库：

<?php
$servername = "localhost";
$username = "username";
$password = "password"; 
// 创建连接
$conn = new mysqli($servername, $username, $password);
// 检测连接
if ($conn->connect_error) {
    die("连接失败: " . $conn->connect_error);
}  
// 创建数据库
$sql = "CREATE DATABASE myDB";
if ($conn->query($sql) === TRUE) {
    echo "数据库创建成功";
} else {
    echo "Error creating database: " . $conn->error;
} 
$conn->close();
?>

创建数据表

<?php
$servername = "localhost";
$username = "username";
$password = "password";
$dbname = "myDB";

// 创建连接
$conn = new mysqli($servername, $username, $password,   $dbname);
// 检测连接
if ($conn->connect_error) {
    die("连接失败: " . $conn->connect_error);
}

// 使用 sql 创建数据表
$sql = "CREATE TABLE MyGuests (
id INT(6) UNSIGNED AUTO_INCREMENT PRIMARY KEY,
firstname VARCHAR(30) NOT NULL,
lastname VARCHAR(30) NOT NULL,
email VARCHAR(50),
reg_date TIMESTAMP
)";

if ($conn->query($sql) === TRUE) {
    echo "Table MyGuests created successfully";
} else {
    echo "创建数据表错误: " . $conn->error;
}

$conn->close();
?> 

插入数据

 <?php
$servername = "localhost";
$username = "username";
$password = "password";
$dbname = "myDB";

// 创建连接
$conn = new mysqli($servername, $username, $password,     $dbname);
// 检测连接
if ($conn->connect_error) {
    die("连接失败: " . $conn->connect_error);
}

$sql = "INSERT INTO MyGuests (firstname, lastname, email)
VALUES ('John', 'Doe', 'john@example.com')";

if ($conn->query($sql) === TRUE) {
    echo "新记录插入成功";
} else {
    echo "Error: " . $sql . "<br>" . $conn->error;
}

$conn->close();
?>

插入多条数据

<?php
$servername = "localhost";
$username = "username";
$password = "password";
$dbname = "myDB";

// 创建链接
$conn = new mysqli($servername, $username, $password,     $dbname);
// 检查链接
if ($conn->connect_error) {
    die("连接失败: " . $conn->connect_error);
} 

$sql = "INSERT INTO MyGuests (firstname, lastname, email)
VALUES ('John', 'Doe', 'john@example.com');";
$sql .= "INSERT INTO MyGuests (firstname, lastname, email)
VALUES ('Mary', 'Moe', 'mary@example.com');";
$sql .= "INSERT INTO MyGuests (firstname, lastname, email)
VALUES ('Julie', 'Dooley', 'julie@example.com')";

if ($conn->multi_query($sql) === TRUE) {
    echo "新记录插入成功";
} else {
    echo "Error: " . $sql . "<br>" . $conn->error;
}

$conn->close();
?>

MySQLi 预处理语句
以下实例在 MySQLi 中使用了预处理语句，并绑定了相应的参数:
实例 (MySQLi 使用预处理语句)

 <?php
$servername = "localhost";
$username = "username";
$password = "password";
$dbname = "myDB";

// 创建连接
$conn = new mysqli($servername, $username, $password, $dbname);

// 检测连接
if ($conn->connect_error) {
    die("连接失败: " . $conn->connect_error);
}

// 预处理及绑定
$stmt = $conn->prepare("INSERT INTO MyGuests (firstname, lastname, email) VALUES (?, ?, ?)");
$stmt->bind_param("sss", $firstname, $lastname, $email);

// 设置参数并执行
$firstname = "John";
$lastname = "Doe";
$email = "john@example.com";
$stmt->execute();

$firstname = "Mary";
$lastname = "Moe";
$email = "mary@example.com";
$stmt->execute();

$firstname = "Julie";
$lastname = "Dooley";
$email = "julie@example.com";
$stmt->execute();

    echo "新记录插入成功";

    $stmt->close();
    $conn->close();
    ?>

从 MySQL 数据库读取数据

<?php
$servername = "localhost";
$username = "username";
$password = "password";
$dbname = "myDB";

// 创建连接
$conn = new mysqli($servername, $username, $password,     $dbname);
// Check connection
if ($conn->connect_error) {
die("连接失败: " . $conn->connect_error);
} 

$sql = "SELECT id, firstname, lastname FROM MyGuests";
$result = $conn->query($sql);

if ($result->num_rows > 0) {
// 输出数据
    while($row = $result->fetch_assoc()) {
          echo "id: " . $row["id"]. " - Name: " . $row["firstname"]. " " .       $row["lastname"]. "<br>";
    }
} else {
    echo "0 结果";
}
$conn->close();
?>

where语句

<?php
$con=mysqli_connect("localhost","username","password","database"    );
// 检测连接
if (mysqli_connect_errno())
{
    echo "连接失败: " . mysqli_connect_error();
}

$result = mysqli_query($con,"SELECT * FROM Persons
WHERE FirstName='Peter'");

while($row = mysqli_fetch_array($result))
{
    echo $row['FirstName'] . " " . $row['LastName'];
    echo "<br>";
}
?>

ORDER BY 关键词

• ORDER BY 关键词用于对记录集中的数据进行排序。
• ORDER BY 关键词默认对记录进行升序排序。
  -用 DESC 关键字降序排序
  语法
  SELECT column_name(s)
  FROM table_name
  ORDER BY column_name(s) ASC|DESC

更新数据库中的数据update

• UPDATE 语句用于更新数据库表中已存在的记录。
  语法
  UPDATE table_name
  SET column1=value, column2=value2,…
  WHERE some_column=some_value

删除数据库中的数据delete

• DELETE FROM 语句用于从数据库表中删除记录。
  语法
  DELETE FROM table_name
  WHERE some_column = some_value