php查询数据库有哪些方法

在PHP中查询数据库，主要有以下几种方法：

1. MySQLi（MySQL Improved Extension）：MySQLi 是一个用于操作 MySQL 数据库的 PHP 扩展。它提供了面向对象和过程式的接口来执行 SQL 查询、管理数据库连接等。

   • 面向对象的用法：

     $conn = new mysqli("localhost", "username", "password", "database");
     if ($conn->connect_error) {
         die("连接失败: " . $conn->connect_error);
     }
     $sql = "SELECT * FROM table_name";
     $result = $conn->query($sql);
     if ($result->num_rows > 0) {
         while($row = $result->fetch_assoc()) {
             echo "id: " . $row["id"]. " - Name: " . $row["name"]. "<br>";
         }
     } else {
         echo "0 结果";
     }
     $conn->close();
     

   • 过程式的用法：

     $conn = mysqli_connect("localhost", "username", "password", "database");
     if (!$conn) {
         die("连接失败: " . mysqli_connect_error());
     }
     $sql = "SELECT * FROM table_name";
     $result = mysqli_query($conn, $sql);
     if (mysqli_num_rows($result) > 0) {
         while($row = mysqli_fetch_assoc($result)) {
             echo "id: " . $row["id"]. " - Name: " . $row["name"]. "<br>";
         }
     } else {
         echo "0 结果";
     }
     mysqli_close($conn);
     

2. PDO（PHP Data Objects）：PDO 是一个在 PHP 中访问数据库的轻量级、一致的接口。支持多种数据库类型，如 MySQL、PostgreSQL、SQLite 等。使用 PDO可以使你更方便地在不同的数据库之间切换。

   try {
       $conn = new PDO("mysql:host=localhost;dbname=database", "username", "password");
       $conn->setAttribute(PDO::ATTR_ERRMODE, PDO::ERRMODE_EXCEPTION);
       $stmt = $conn->prepare("SELECT * FROM table_name");
       $stmt->execute();
       $result = $stmt->setFetchMode(PDO::FETCH_ASSOC);
       foreach($stmt->fetchAll() as $row) {
           echo "id: " . $row["id"]. " - Name: " . $row["name"]. "<br>";
       }
   } catch(PDOException $e) {
       echo "连接失败: " . $e->getMessage();
   }
   $conn = null;
   

3. SQL Server：对于 SQL Server 数据库，可以使用 sqlsrv 扩展或 PDO_SQLSRV 驱动程序。

   • 使用 sqlsrv 扩展（面向对象）：

     $conn = new sqlsrv\Connection("server=localhost;Database=database", "username", "password");
     $conn->connect();
     $tsql = "SELECT * FROM table_name";
     $getResults = $conn->query($tsql);
     if ($getResults == FALSE) {
         die(print_r($conn->errors, true));
     }
     while ($row = $getResults->fetchArray()) {
         echo "id: " . $row['id'] . " - Name: " . $row['name'] . "<br>";
     }
     $conn->close();
     

   • 使用 sqlsrv 扩展（过程式）：

     $conn = sqlsrv_connect("server=localhost;Database=database", array("Database" => "database", "Uid" => "username", "PWD" => "password"));
     if (!$conn) {
         die(print_r(sqlsrv_errors(), true));
     }
     $tsql = "SELECT * FROM table_name";
     $getResults = sqlsrv_query($conn, $tsql);
     if ($getResults === FALSE) {
         die(print_r(sqlsrv_errors(), true));
     }
     while ($row = sqlsrv_fetch_array($getResults, SQLSRV_FETCH_ASSOC)) {
         echo "id: " . $row['id'] . " - Name: " . $row['name'] . "<br>";
     }
     sqlsrv_free_stmt($getResults);
     sqlsrv_close($conn);
     

   • 使用 PDO_SQLSRV 驱动程序（面向对象）：

     try {
         $conn = new PDO("sqlsrv:server=localhost;Database=database", "username", "password");
         $conn->setAttribute(PDO::ATTR_ERRMODE, PDO::ERRMODE_EXCEPTION);
         $stmt = $conn->prepare("SELECT * FROM table_name");
         $stmt->execute();
         $result = $stmt->setFetchMode(PDO::FETCH_ASSOC);
         foreach($stmt->fetchAll() as $row) {
             echo "id: " . $row["id"]. " - Name: " . $row["name"]. "<br>";
         }
     } catch(PDOException $e) {
         echo "连接失败: " . $e->getMessage();
     }
     $conn = null;
     

4. Oracle：对于 Oracle 数据库，可以使用 oci8 扩展。

   $conn = oci_connect("username", "password", "//localhost/dbname");
   if (!$conn) {
       $e = oci_error();
       trigger_error(htmlentities($e['message'], ENT_QUOTES), E_USER_ERROR);
   }
   $sql = "SELECT * FROM table_name";
   $result = oci_parse($conn, $sql);
   if (!$result) {
       $e = oci_error($conn);
       trigger_error(htmlentities($e['message'], ENT_QUOTES), E_USER_ERROR);
   }
   oci_execute($result);
   while ($row = oci_fetch_assoc($result)) {
       echo "id: " . $row["id"]. " - Name: " . $row["name"]. "<br>";
   }
   oci_free_statement($result);
   oci_close($conn);
   

这些方法都可以用于查询数据库，具体选择哪种方法取决于你的需求和项目类型。如果你需要在多个数据库之间切换，建议使用 PDO。