PHP 笔记——操作MySQL数据库

1. 连接MySQL服务器

​ mysqli_connect ：此函数是该函数的别名： mysqli::__construct()

mysqli mysqli_connect ( [string server [, string username [,
string password [, string dbname [, int port [, string socket]]]]]] )

参数	说明
server	MySQL服务器地址（host）
username	用户名
password	密码
dbname	连接的数据库名称
port	MySQL服务器使用的端口号
socket	UNIX域socket

<?php
    $host = "127.0.0.1";            //MySQL服务器地址
    $userName = "root";             //用户名
    $password = "root";             //密码
    if ($connID = mysqli_connect($host, $userName, $password)){
        echo "<script type='text/javascript'>alert('数据库连接成功！');</script>";
    }else{
        echo "<script type='text/javascript'>alert('数据库连接失败！');</script>";
    }
?>

为了屏蔽由于数据库连接失败而显示的不友好的错误信息，可以在 mysqli_connect () 函数前加 “@” 来屏蔽错误提示。

<?php
    $host = "127.0.0.1";            //MySQL服务器地址
    $userName = "root";             //用户名
    $password = "111";              //密码
    if ($connID = @mysqli_connect($host, $userName, $password)){
        echo "<script type='text/javascript'>alert('数据库连接成功！');</script>";
    }else{
        echo "<script type='text/javascript'>alert('数据库连接失败！');</script>";
    }
?>

2. 选择MySQL数据库

（1）mysqli_connect

$connID = mysqli_connect("127.0.0.1", "root", "111", "mysql");

（2）mysqli_select_db

bool mysqli_select_db ( mysqli $link , string $dbname )

参数	说明
link	仅以过程化样式：由mysqli_connect() 或 mysqli_init() 返回的链接标识。
dbname	数据库名称

<?php
    $host = "127.0.0.1";            //MySQL服务器地址
    $userName = "root";             //用户名
    $password = "root";             //密码
    $dbName = "mysql";              //数据库名称
    //建立与MySQL数据库服务器的连接，并选择数据库
    $connID = mysqli_connect($host, $userName, $password);
    if(mysqli_select_db($connID, $dbName)){
        echo "数据库选择成功！";
    }else{
        echo "数据库选择失败！"; 
    }
?> 

3. 执行SQL语句

mixed mysqli_query( mysqli link, string query [, int resultmode] )

参数	说明
link	仅以过程化样式：由mysqli_connect() 或 mysqli_init() 返回的链接标识。
query	sql语句
resultmode

//连接MySQL服务器，选择数据库
$conn = mysqli_connect("localhost", "root", "root", "stu") or die("连接数据库服务器失败！" . mysqli_error());
//设置数据库编码格式utf8
mysqli_query($conn, "set names utf8");

mysqli_query($conn, "insert into users values('4', '张三', '男', '23')");
mysqli_query($conn, "update users set  Name='张三' where Id='1'");
mysqli_query($conn, "delete from users where Id='211789111'"); 
mysqli_query($conn, "use stu");
mysqli_query($conn, "set names utf8");
$result = mysqli_query($conn, "select * from users");

4. 将结果集返回到数组中

array mysqli_fetch_array ( resource result [, int result_type] )

参数	说明
result	由 mysqli_query()函数返回的数据指针
result_type	设置结果集数组的表达方式。 - MYSQL_ASSOC：关联数组 - MYSQL_NUM：数字数组 - MYSQL_BOTH：默认。同时产生关联和数字数组。

<?php   
    while($myrow = mysqli_fetch_array($result)){
?>
    <tr>
        <td align="center"><span><?php echo $myrow[0]; ?></span></td>
        <td align="center"><span><?php echo $myrow[1]; ?></span></td>
        <td align="center"><span><?php echo $myrow[2]; ?></span></td>
        <td align="center"><span><?php echo $myrow[3]; ?></span></td>
    </tr>
    <br>
<?php
    }
?> 

5. 从结果集中获取一行作为对象

mixed mysqli_fetch_object ( resource result )

<?php   
    while($myrow = mysqli_fetch_object($result)){
?>
    <tr>
        <td align="center"><span><?php echo $myrow->Id; ?></span></td>
        <td align="center"><span><?php echo $myrow->Name; ?></span></td>
        <td align="center"><span><?php echo $myrow->Sex; ?></span></td>
        <td align="center"><span><?php echo $myrow->Age; ?></span></td>
    </tr>
    <br>
<?php
    }
?> 

6. 从结果集中获取一行作为枚举数组

mixed mysqli_fetch_row ( resource result )

<?php   
    while($myrow = mysqli_fetch_row($result)){
?>
    <tr>
        <td align="center"><span><?php echo $myrow[0]; ?></span></td>
        <td align="center"><span><?php echo $myrow[1]; ?></span></td>
        <td align="center"><span><?php echo $myrow[2]; ?></span></td>
        <td align="center"><span><?php echo $myrow[3]; ?></span></td>
    </tr>
    <br>
<?php
    }
?> 

7. 从结果集中获取一行作为关联数组

mixed mysqli_fetch_assoc ( resource result )

<?php
    while($myrow = mysqli_fetch_assoc($result)){
?>
    <tr>
        <td align="center"><span><?php echo $myrow['Id']; ?></span></td>
        <td align="center"><span><?php echo $myrow['Name']; ?></span></td>
        <td align="center"><span><?php echo $myrow['Sex']; ?></span></td>
        <td align="center"><span><?php echo $myrow['Age']; ?></span></td>
    </tr>
    <br>
<?php
    }
?> 

8. 获取查询结果集中的记录数

int mysqli_num_rows ( resource result )

$nums = mysqli_num_rows ( $result );
echo $nums;

9. 释放内存

void mysqli_free_result(resource result)

10. 关闭连接

bool mysqli_close ( mysqli link )

mysqli_free_result($result);        // 释放内存
mysqli_close($conn);                // 关闭连接

11. 连接与关闭MySQL服务器的最佳时机

function book_query(){
    global $conn;
    $result = mysqli_query($conn,"select * from tb_demo01");
    while($myrow = mysqli_fetch_row($result)){
        echo $myrow[1]." ";
        echo $myrow[2]."<br />";
    }
    mysqli_free_result($result);
}

$conn = mysqli_connect("localhost", "root", "111", "db_database10")
or die("连接数据库服务器失败！".mysqli_error());
mysqli_query($conn,"set names utf8");
book_query();
book_query();
mysqli_close($conn);