mysqli::select_db

mysqli_select_db

(PHP 5)

mysqli::select_db -- mysqli_select_db — Selects the default database for database queries

说明

面向对象风格

bool mysqli::select_db ( string $dbname )

过程化风格

bool mysqli_select_db ( mysqli $link , string $dbname )

Selects the default database to be used when performing queries against the database connection.

Note:
This function should only be used to change the default database for the connection. You can select the default database with 4th parameter in mysqli_connect().

参数

link: 仅以过程化样式：由 mysqli_connect() 或 mysqli_init() 返回的链接标识。
dbname: The database name.

返回值

成功时返回 TRUE，或者在失败时返回 FALSE.

范例

Example #1 mysqli::select_db() example

面向对象风格


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

/* check connection */
if (mysqli_connect_errno()) {
    printf("Connect failed: %s\n", mysqli_connect_error());
    exit();
}

/* return name of current default database */
if ($result = $mysqli->query("SELECT DATABASE()")) {
    $row = $result->fetch_row();
    printf("Default database is %s.\n", $row[0]);
    $result->close();
}

/* change db to world db */
$mysqli->select_db("world");

/* return name of current default database */
if ($result = $mysqli->query("SELECT DATABASE()")) {
    $row = $result->fetch_row();
    printf("Default database is %s.\n", $row[0]);
    $result->close();
}

$mysqli->close();
?>

过程化风格


<?php
$link = mysqli_connect("localhost", "my_user", "my_password", "test");

/* check connection */
if (mysqli_connect_errno()) {
    printf("Connect failed: %s\n", mysqli_connect_error());
    exit();
}

/* return name of current default database */
if ($result = mysqli_query($link, "SELECT DATABASE()")) {
    $row = mysqli_fetch_row($result);
    printf("Default database is %s.\n", $row[0]);
    mysqli_free_result($result);
}

/* change db to world db */
mysqli_select_db($link, "world");

/* return name of current default database */
if ($result = mysqli_query($link, "SELECT DATABASE()")) {
    $row = mysqli_fetch_row($result);
    printf("Default database is %s.\n", $row[0]);
    mysqli_free_result($result);
}

mysqli_close($link);
?>

以上例程会输出：

Default database is test.
Default database is world.

参见

mysqli_connect() - 别名 mysqli::__construct
mysqli_real_connect() - Opens a connection to a mysql server

add a note User Contributed Notes mysqli::select_db

pjasiulewicz at gmail dot com 27-Mar-2011 02:30


In some situations its useful to use this function for changing databases in general. We've tested it in production environment and it seams to be faster with switching databases than creating new connections.

add a note