PHP mysqli select_db() 函数

定义和用法

select_db() / mysqli_select_db() 函数用于更改连接的默认数据库。

实例

例子 1 - 面向对象风格

更改连接的默认数据库：

<?php
$mysqli = new mysqli("localhost","my_user","my_password","my_db");

if ($mysqli -> connect_errno) {
  echo "Failed to connect to MySQL: " . $mysqli -> connect_error;
  exit();
}

// 返回当前默认数据库的名称
if ($result = $mysqli -> query("SELECT DATABASE()")) {
  $row = $result -> fetch_row();
  echo "Default database is " . $row[0];
  $result -> close();
}

// 将数据库更改为 "test" 数据库
$mysqli -> select_db("test");

// 返回当前默认数据库的名称
if ($result = $mysqli -> query("SELECT DATABASE()")) {
  $row = $result -> fetch_row();
  echo "Default database is " . $row[0];
  $result -> close();
}

$mysqli -> close();
?>

例子 2 - 过程式风格

更改连接的默认数据库：

<?php
$con=mysqli_connect("localhost","my_user","my_password","my_db");

if (mysqli_connect_errno()) {
  echo "Failed to connect to MySQL: " . mysqli_connect_error();
  exit;
}

// 返回当前默认数据库的名称
if ($result = mysqli_query($con, "SELECT DATABASE()")) {
  $row = mysqli_fetch_row($result);
  echo "Default database is " . $row[0];
  mysqli_free_result($result);
}

// 将数据库更改为 "test" 数据库
mysqli_select_db($con, "test");

// 返回当前默认数据库的名称
if ($result = mysqli_query($con, "SELECT DATABASE()")) {
  $row = mysqli_fetch_row($result);
  echo "Default database is " . $row[0];
  mysqli_free_result($result);
}

// 关闭连接
mysqli_close($con);
?>

语法

面向对象风格：

$mysqli -> select_db(name)

过程式风格：

mysqli_select_db(connection, name)

技术细节