php操作mysql（数据库常规操作）

php操作数据库八步走

<?php
    // 1、建立连接
    $connection = mysqli_connect("127.0.0.1", "root", "123456");

    // 2、判断连接是否成功
    if (mysqli_connect_error() != null) {
        die(mysqli_connect_error());
    } else {
        echo "连接成功！";
    }

    ///3、选择数据库
    mysqli_select_db($connection, "test");

    ///4、设置字符集
    mysqli_set_charset($connection, "utf8");

    ///5、书写 SQL 语句
    $sql = "SELECT * FROM `user` LIMIT 1";

    ///6、执行 SQL 语句
    $result = mysqli_query($connection, $sql);

    ///7、解析结果集
    $array = mysqli_fetch_array($result, MYSQLI_BOTH);

    ///8、关闭连接
    mysqli_close($connection);

添加、更新、删除数据

<?php
// 连接数据库
$link = mysqli_connect("127.0.0.1", "root", "123456");

// 判断数据库连接是否成功
if (!is_null(mysqli_connect_error())) {
    die(mysqli_connect_error());
}

// 选择数据库
mysqli_select_db($link, "test");

// 设置连接字符集
mysqli_set_charset($link, "utf8");

// 书写 SQL 语句
// $sql = "INSERT INTO `user` (`username`, `password`) VALUES("user-5", "password-5")";//增加数据
// $sql = "UPDATE user SET password="password" WHERE id > 4";//修改数据
$sql = "DELETE FROM user WHERE id > 4";//删除数据

// 执行 SQL 语句
$result = mysqli_query($link, $sql);

// 解析 SQL 语句执行结果
if ($result) {
    echo "执行成功！"
     . " 成功删除了数据 " . mysqli_affected_rows($link) . " 条！";
     // . " 插入数据的 ID 是 " . mysqli_insert_id($link) . "。";
} else {
    echo "执行失败！";
}

// 关闭连接，释放资源
mysqli_close($link);

简单查询和数据解析

<?php
    // 建立连接
    $link = mysqli_connect("127.0.0.1", "root", "123456");

    // 判断连接是否成功
    if (mysqli_connect_error() != null) {
        die(mysqli_connect_error());
    }

    // 选择数据库
    mysqli_select_db($link, "test");

    // 设置字符集
    mysqli_set_charset($link, "utf8");

    // 书写 SQL 语句
    $sql = "SELECT good, class, price, stock FROM good WHERE id < 4";

    // 执行 SQL 语句
    $result = mysqli_query($link, $sql);

    // 解析结果集
    echo "<pre>";
     $data = mysqli_fetch_array($result);
     var_dump($data);

     while ($row = mysqli_fetch_array($result, MYSQLI_BOTH)) {
         var_dump($row);//使用或输出所有查询的数据
     }

     while ($row = mysqli_fetch_row($result)) {
         var_dump($row);//把查询结果返回到一个数组中，用数字索引取值
     }

     while ($row = mysqli_fetch_assoc($result)) {
         var_dump($row);//把查询结果返回到一个数组中，用关键字索引取值
     }

     while ($row = mysqli_fetch_object($result)) {
         var_dump($row);//从结果集中取得当前行，并作为对象返回
     }

     $data = mysqli_fetch_all($result, MYSQLI_BOTH);//从结果集中取得所有行作为关联数组
     var_dump($data);

     $num = mysqli_num_rows($result);
     echo "共查询到 " . $num . " 条数据！";
     $num = mysqli_num_fields($result);
     echo "共查询到 " . $num . " 列数据！";

    // 关闭连接
    mysqli_close($link);

复杂查询

<?php
    // 建立连接
    $link = mysqli_connect("127.0.0.1", "root", "123456");

    // 判断连接是否成功
    if (mysqli_connect_error() != null) {
        die(mysqli_connect_error());
    }

    // 选择数据库
    mysqli_select_db($link, "test");

    // 设置字符集
    mysqli_set_charset($link, "utf8");

    // 书写 SQL 语句
    $sql = "SELECT good.*, class.class FROM good, class WHERE good.class = class.id AND good.stock >= 25 AND good.price <= 50 AND good.class = 4 ORDER BY good.price ASC LIMIT 6";

    // 执行 SQL 语句
    $result = mysqli_query($link, $sql);

    // 解析结果集
    echo "<table border="1">";
    echo "<tr>";
    echo "<th>IDth>";
    echo "<th>商品th>";
    echo "<th>类别th>";
    echo "<th>单价th>";
    echo "<th>库存th>";
    echo "<th>更新时间th>";
    echo "<th>创建时间th>";
    echo "tr>";
    while ($row = mysqli_fetch_assoc($result)) {
        echo "<tr>";
        echo "<td width="100px">" . $row["id"] . "td>";
        echo "<td width="100px">" . $row["good"] . "td>";
        echo "<td width="100px">" . $row["class"] . "td>";
        echo "<td width="100px">" . $row["price"] . "td>";
        echo "<td width="100px">" . $row["stock"] . "td>";
        echo "<td width="100px">" . $row["updated_at"] . "td>";
        echo "<td width="100px">" . $row["created_at"] . "td>";
        echo "tr>";
    }
    echo "table>";

    // 关闭连接
    mysqli_close($link);

程序错误排查

<?php
    // 建立连接
    $link = mysqli_connect("127.0.0.1", "root", "123456");

    // 判断连接是否成功
    if (mysqli_connect_error() != null) {
        die(mysqli_connect_error());
    }

    // 选择数据库
    mysqli_select_db($link, "test");

    // 设置字符集
    mysqli_set_charset($link, "utf8");

    // 书写 SQL 语句
    // $sql = "SELECT * FROM good ORDER BY price ASC GROUP BY class";
    $sql = "INSERT INTO good (good, class, price, stock) VALUES("test", "test", 20, 56)";
    // $sql = "INSERT INTO class(class) VALUES("水果")";

    // 执行 SQL 语句
    $result = mysqli_query($link, $sql);

    // 解析结果集
    // var_dump($result);
    $error = mysqli_error($link);
    $errno = mysqli_errno($link);

    echo "SQL 语句执行失败！错误代码：" . $errno . "，错误信息：" . $error;

    // 关闭连接
    mysqli_close($link);