执行环境 WAMP

mysql_connect

数据库连接

test.php

<?php
        header("Content-type:text/html;charset=utf-8");
        if($con=mysql_connect('localhost','root','')){
            echo '连接成功';
        }else{
            echo '连接失败';
        }
?>

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数据库扩展

$link = mysql_connect('mysql_host', 'mysql_user', 'mysql_password');

mysqli扩展

$link = mysqli_connect('mysql_host', 'mysql_user', 'mysql_password');

PDO扩展

$dsn = 'mysql:dbname=testdb;host=127.0.0.1';
$user = 'dbuser';
$password = 'dbpass';
$dbh = new PDO($dsn, $user, $password);

mysql_close

if($con=mysql_connect('localhost','root','')){
    echo '连接成功';
}else{
    echo '连接失败';
}
echo mysql_close($con);//1

mysql_select_db

<?php
header("Content-type:text/html;charset=utf-8");
if($con=mysql_connect('localhost','root','')){
   echo '连接成功'."<br/>";
}else{
   echo '连接失败'."<br/>";
 }
if(mysql_select_db('info')){
   echo "选择数据库成功";
 }else{
   echo "选择数据库失败";
 }
?>

连接成功
选择数据库成功

<?php
   header("Content-type:text/html;charset=utf-8");
   $host = '127.0.0.1';
   $user = 'root';
   $pass = '';
   //在这里编写数据库连接代码
   echo $link=mysql_connect($host,$user,$pass);//Resource id #3
   echo mysql_select_db('info');//1
   echo mysql_query("set names 'utf8'");//1  设置当前连接使用的字符编码
?>

mysql_query

<?php
header("Content-type:text/html;charset=utf-8");
if ($con = mysql_connect('localhost', 'root', '')) {
    echo '连接成功' . "<br/>";
} else {
    echo '连接失败' . "<br/>";
}

if (mysql_select_db('info')) {
    echo "选择数据库成功"."<br/>";
} else {
    echo "选择数据库失败"."<br/>";
}

if(mysql_query('insert into test(name) values("abc")')){
    echo '插入成功';
}else{
    echo "插入失败";
}
mysql_close($con);
?>

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连接成功
选择数据库成功
插入成功

$res = mysql_query('select * from user limit 1');
$row = mysql_fetch_array($res);
var_dump($row);

array
  0 => string '1' (length=1)
  'id' => string '1' (length=1)
  1 => string 'abc' (length=3)
  'name' => string 'abc' (length=3)

多个连接

$link1 = mysql_connect('127.0.0.1', 'code1', '');
$link2 = mysql_connect('127.0.0.1', 'code1', '', true); //开启一个新的连接
$res = mysql_query('select * from user limit 1', $link1); //从第一个连接中查询数据

在mysql中，执行插入语句以后，可以得到自增的主键id,通过PHP的mysql_insert_id函数可以获取该id。

$uid = mysql_insert_id();

这个id的作用非常大，通常可以用来判断是否插入成功，或者作为关联ID进行其他的数据操作。

smysql_error()

echo mysql_error();

$name = '李四';
$age = 18;
$class = '高三一班';
$sql = "insert into user(name, age, class) values('$name', '$age', '$class')";
mysql_query($sql); //执行插入语句

You have an error in your SQL syntax; check the manual that corresponds to 
your MySQL server version for the right syntax to use near 'insert2 into 
test(name) values("abc")' at line 1插入失败

mysql_insert_id()

<?php
    mysql_connect('127.0.0.1','root','');
    mysql_select_db('info');
    mysql_query("set names 'utf8'");
    $name='李四';
    $age=18;
    $class='高三一班';
    $sql="insert into test(name) values('$name')";
    mysql_query($sql);
    $uid=mysql_insert_id();
    echo $uid;//返回插入的id
?>