array ( 0 => 'index.php', 1 => 'PHP Manual', ), 'head' => array ( 0 => 'UTF-8', 1 => 'zh', ), 'this' => array ( 0 => 'mysqli.select-db.php', 1 => 'mysqli::select_db', ), 'up' => array ( 0 => 'class.mysqli.php', 1 => 'mysqli', ), 'prev' => array ( 0 => 'mysqli.savepoint.php', 1 => 'mysqli::savepoint', ), 'next' => array ( 0 => 'mysqli.set-charset.php', 1 => 'mysqli::set_charset', ), 'alternatives' => array ( ), 'source' => array ( 'lang' => 'zh', 'path' => 'reference/mysqli/mysqli/select-db.xml', ), ); $setup["toc"] = $TOC; $setup["toc_deprecated"] = $TOC_DEPRECATED; $setup["parents"] = $PARENTS; manual_setup($setup); ?>
(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。
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");
/* 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.