(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
面向对象风格
过程化风格
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。
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
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 #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");
$result = $mysqli->query("SELECT DATABASE()");
$row = $result->fetch_row();
printf("Default database is %s.\n", $row[0]);
$mysqli->select_db("world");
$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");
$result = mysqli_query($link, "SELECT DATABASE()");
$row = mysqli_fetch_row($result);
printf("Default database is %s.\n", $row[0]);
mysqli_select_db($link, "world");
$result = mysqli_query($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.