增删改查

<?php
header("Content-type:text/html; charset=utf-8");
    //创建数据库
    $servername = "localhost:3306";
    $username = "root";
    $password = "";
    $dbname = "db3"; 
    $sql = "CREATE DATABASE $dbname DEFAULT CHARACTER SET utf8 COLLATE utf8_general_ci";
    $conn = new mysqli($servername,$username,$password);//在创建数据库时,不要写第四个数据库名称的参数
    if($conn->query($sql) === TRUE)
     {
         echo "数据库创建成功";
     }else
     {
         echo "数据库创建失败:".$conn->error;
     }
    //删除数据库
/*     $sql = "DROP DATABASE $dbname";
    $conn = new mysqli($servername,$username,$password);
    if($conn->query($sql)===TRUE)
    {
        echo "数据库删除成功";
    }else
    {
        echo "数据库删除失败:".$conn->error;
    } */
    $conn = new mysqli($servername,$username,$password,$dbname);
    //设置连接字符集编码
    $sql = "SET CHARACTER SET 'UTF8'";
    $conn->query($sql);
    //告诉服务器将来从这个客户端传来的信息采用字符集utf8;
    $sql = "SET NAMES 'UTF8'";
    $conn ->query($sql);
    
    
    //==================================
    //创建数据表（创建数据表的前提是，必须连接到数据库）
    $sql = "CREATE TABLE UserList(
    id INT(6) UNSIGNED AUTO_INCREMENT PRIMARY KEY,
    name VARCHAR(60) NOT NULL,
    height INT(6) NOT NULL,
    weight decimal(10,4),
    date1 TIMESTAMP,
    nation VARCHAR(60),
    sex VARCHAR(60),
    like1 VARCHAR(60),
    intro VARCHAR(60))
    ENGINE = MYISAM DEFAULT CHARSET = utf8";
    //decimal(10,6)，数值中共有10位数，其中整数占4位，小数占6位    
    if($conn->query($sql)===TRUE)
    {
        echo "创建数据表成功<br>";
    }else
    {
        echo "创建数据表失败:" .$conn->error;
    }
    //删除数据表
/*     $sql = "DROP TABLE UserList";
    if($conn->query($sql)===TRUE)
    {
        echo "删除数据表成功<br>"; 
    }else
    {
        echo "<br>删除数据表错误:".$coon->error;
    } */
    //插入数据
    //$ip=$_SERVER["REMOTE_ADDR"];
    $sql = "insert into UserList
    (name,height,weight,date1,nation,sex,like1,intro) values('name',1,2,now(),'a','a','a','intro')";
    if($conn->query($sql)===TRUE)
    {
        echo "<span style='color:green;'>"."数据插入成功"."</span><br>";
    }else
    {
        echo "<br>数据插入失败<br>";
    }
    echo mysqli_insert_id($conn);//取出插⼊入的数据的编号
    //删除数据
    $sql = "delete from UserList";
    if($conn->query($sql)===TRUE)
    {
        echo "数据删除成功<br>";
    }else
    {
        echo "数据删除失败<br>";
    }
    echo "受影响的行数:".mysqli_affected_rows($conn);
    
    //========================
    //修改
    $sql = "update UserList set name = '新名词',height =200 where id>=2<=6";
    if($conn->query($sql)===TRUE)
    {
        echo "数据修改成功<br>";
    }else
    {
        echo "数据修改失败<br>";
    }
    echo "受影响的行数:".mysqli_affected_rows($conn);//如果没有造成事实上的修改，就返回0;
    
    //+========================
    //$sql = "SELECT id ,name,date1,height FROM UserList where height>10";
    $sql = "select*from UserList order by id asc limit 2,5";//从下标2开始，取回5条数据;
    $result = $conn->query($sql);
    //fetch_assoc()函数从结果集中取得一行作为关联数组。
    //返回根据从结果集取得的生成的关联数组，如果没有 更多行，就会返回false;
    while ($row = $result->fetch_assoc())
    {
        echo "<br>id:".$row["id"]."-name:".$row["name"]."".$row["height"];
    }
    echo "<br>受影响的行数:".mysqli_affected_rows($conn)."<br>";
    
    //关闭打开的数据库;
    $conn->close();