php日记——使用mysqli_$conn->query($sql)-优快云博客

这篇博客介绍了如何使用PHP的mysqli扩展来操作MySQL数据库，包括创建数据库、查看数据库、创建表、插入数据、查询数据和修改数据的基本步骤。通过实例代码展示了mysqli的用法，并提醒读者可以通过预处理和绑定来提高安全性。

首先你要确保你启动了MYSQL

记住启动的端口号（通常是3306）

现在开始php的mysqli之旅

首先当然是创建数据库

<?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("Connection failed: " . $conn->connect_error);
} 

// Create database
$sql = "CREATE DATABASE myDB";
if ($conn->query($sql) === TRUE) {
    echo "Database created successfully";
} else {
    echo "Error creating database: " . $conn->error;
}

$conn->close();
?>

创建成功之后

可以进入mysql查看是否已经创建

如果配置好的话

到cmd中输入mysql -uroot -p

如果mysql没添加到环境变量的话

右键+shift键

然后点击此处用命令窗口打开

然后再输入上面那条命令

然后输入密码

然后可以输入命令

show databases;(别忘了分号)

如果成功创建的话会发现有myDB这个数据库

不熟悉的sql命令的同学可先点开下面的链接去看看常用的sql命令

http://blog.youkuaiyun.com/jenny0107/article/details/1332815

创建数据库之后就是创建表

因为我们已经创建了数据库，所以连接时把数据库的名字加上

全部代码改为

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

// 创建连接
$conn = mysqli_connect($servername, $username, $password, $dbname);
// 检测连接
if (!$conn) {
    die("Connection failed: " . mysqli_connect_error());
}

// sql to create table
$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 (mysqli_query($conn, $sql)) {
    echo "Table MyGuests created successfully";
} else {
    echo "Error creating table: " . mysqli_error($conn);
}

mysqli_close($conn);
?>

可以到mysql命令行里查看这个表

首先输入use myDB;

然后输入show tables;

这样就可以看到有表myGuests

创建表之后就是插入数据了

将代码换为

<?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("Connection failed: " . $conn->connect_error);
} 

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

if ($conn->query($sql) === TRUE) {
    echo "New record created successfully";
} else {
    echo "Error: " . $sql . "<br>" . $conn->error;
}

$conn->close();
?>

如果想多条插入

<?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("Connection failed: " . $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 "New records created successfully";
} else {
    echo "Error: " . $sql . "<br>" . $conn->error;
}

$conn->close();
?>

如果有很多条插入的话，使用预处理加绑定会比较清晰而且方便

<?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("Connection failed: " . $conn->connect_error);
}

// prepare and bind
$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 "New records created successfully";

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

如果想在mysql里查看数据的话

在mysql命令模式里（已经进入myDB这个数据库）

输入select * from myGuests;

这样就可以显示myGuests表里的全部数据了

然后就是获取表里的数据

将代码换为

<?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("Connection failed: " . $conn->connect_error);
} 

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

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

其实查询的核心语句是

select * from 数据表 where 字段名=字段值
可以将*换成想要读取的字段，*代表读取全部字段

我是建议直接用*的，等输出时再输出想要的字段值就是了

where后接的是条件，多个条件有and连接，注意空格

至于改的话

代码是

<?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("Connection failed: " . $conn->connect_error);
}

$sql = "UPDATE MyGuests SET email='jkgeekjk@163.com' WHERE firstname='John' AND LastName='Doe'";

$result = $conn->query($sql);


$conn->close();
?>

删除的话

代码为

<?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("Connection failed: " . $conn->connect_error);
}

$sql = "DELETE FROM MyGuests WHERE LastName='Griffin'";

$result = $conn->query($sql);


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