mysqli::select_db

mysqli_select_db

(PHP 5, PHP 7, PHP 8)

mysqli::select_db -- mysqli_select_db — 选择用于数据库查询的默认数据库

说明

面向对象风格

public mysqli::select_db(string $database): bool

过程化风格

mysqli_select_db(mysqli $mysql, string $database): bool

选择默认数据库，用于在已连接的数据库中执行查询。

注意:

此函数只能用于更改连接的默认数据库。可以在 mysqli_connect() 中使用第 4 个参数选择默认数据库。

参数

mysql

仅以过程化样式：由 mysqli_connect() 或 mysqli_init() 返回的 mysqli 对象。

database

数据库名称

返回值

成功时返回 true， 或者在失败时返回 false。

错误／异常

If mysqli error reporting is enabled (MYSQLI_REPORT_ERROR) and the requested operation fails, a warning is generated. If, in addition, the mode is set to MYSQLI_REPORT_STRICT, a mysqli_sql_exception is thrown instead.

示例

示例 #1 mysqli::select_db() 示例

面向对象风格

<?php

mysqli_report(MYSQLI_REPORT_ERROR | MYSQLI_REPORT_STRICT);
$mysqli = new mysqli("localhost", "my_user", "my_password", "test");

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

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

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

过程化风格

<?php

mysqli_report(MYSQLI_REPORT_ERROR | MYSQLI_REPORT_STRICT);
$link = mysqli_connect("localhost", "my_user", "my_password", "test");

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

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

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

以上示例会输出：

Default database is test.
Default database is world.

参见