PHP mysqli select_db() 函数
示例 - 面向对象的样式
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: " . $mysqli -> connect_error;
exit();
}
// Return name of current default database
if ($result = $mysqli -> query("SELECT DATABASE()")) {
$row = $result -> fetch_row();
echo "Default database is " . $row[0];
$result -> close();
}
// Change db to "test" db
$mysqli -> select_db("test");
// Return name of current default database
if ($result = $mysqli -> query("SELECT DATABASE()")) {
$row = $result -> fetch_row();
echo "Default database is " . $row[0];
$result -> close();
}
$mysqli -> close();
?>
$mysqli = new mysqli("localhost","my_user","my_password","my_db");
if ($mysqli -> connect_errno) {
echo "Failed to connect to MySQL: " . $mysqli -> connect_error;
exit();
}
// Return name of current default database
if ($result = $mysqli -> query("SELECT DATABASE()")) {
$row = $result -> fetch_row();
echo "Default database is " . $row[0];
$result -> close();
}
// Change db to "test" db
$mysqli -> select_db("test");
// Return name of current default database
if ($result = $mysqli -> query("SELECT DATABASE()")) {
$row = $result -> fetch_row();
echo "Default database is " . $row[0];
$result -> close();
}
$mysqli -> close();
?>
查看底部的程序样式示例。
定义和用法
select_db() / mysqli_select_db() 函数用于更改连接的默认数据库。
语法
面向对象的风格：
$mysqli ->
select_db(name)
程序风格：
mysqli_select_db(connection, name)
参数值
| 参数 | 描述 |
|---|---|
| connection | 必需。规定要使用的 MySQL 连接。 |
| name | 必需，规定要使用的默认数据库。 |
技术细节
| 返回值: | 若成功则返回 TRUE，若失败则返回 FALSE。 |
|---|---|
| PHP 版本: | 5+ |
示例 - 程序样式
更改连接的默认数据库：
<?php
$con=mysqli_connect("localhost","my_user","my_password","my_db");
if (mysqli_connect_errno()) {
echo "Failed to connect to MySQL: " . mysqli_connect_error();
exit;
}
// Return name of current default database
if ($result = mysqli_query($con, "SELECT DATABASE()")) {
$row = mysqli_fetch_row($result);
echo "Default database is " . $row[0];
mysqli_free_result($result);
}
// Change db to "test" db
mysqli_select_db($con, "test");
// Return name of current default database
if ($result = mysqli_query($con, "SELECT DATABASE()")) {
$row = mysqli_fetch_row($result);
echo "Default database is " . $row[0];
mysqli_free_result($result);
}
// Close connection
mysqli_close($con);
?>
$con=mysqli_connect("localhost","my_user","my_password","my_db");
if (mysqli_connect_errno()) {
echo "Failed to connect to MySQL: " . mysqli_connect_error();
exit;
}
// Return name of current default database
if ($result = mysqli_query($con, "SELECT DATABASE()")) {
$row = mysqli_fetch_row($result);
echo "Default database is " . $row[0];
mysqli_free_result($result);
}
// Change db to "test" db
mysqli_select_db($con, "test");
// Return name of current default database
if ($result = mysqli_query($con, "SELECT DATABASE()")) {
$row = mysqli_fetch_row($result);
echo "Default database is " . $row[0];
mysqli_free_result($result);
}
// Close connection
mysqli_close($con);
?>
