(PHP 5, PHP 7, PHP 8)
mysqli::select_db -- mysqli_select_db — 選擇用于數(shù)據(jù)庫(kù)查詢的默認(rèn)數(shù)據(jù)庫(kù)
面向?qū)ο箫L(fēng)格
$dbname): bool過(guò)程化風(fēng)格
針對(duì)本次數(shù)據(jù)庫(kù)連接用于數(shù)據(jù)庫(kù)查詢的默認(rèn)數(shù)據(jù)庫(kù)。
注意:
本函數(shù)應(yīng)該只被用在改變本次鏈接的數(shù)據(jù)庫(kù)，你也能在mysqli_connect()第四個(gè)參數(shù)確認(rèn)默認(rèn)數(shù)據(jù)庫(kù)。
mysql僅以過(guò)程化樣式：由mysqli_connect() 或 mysqli_init() 返回的 mysqli 對(duì)象。
dbname數(shù)據(jù)庫(kù)名稱
成功時(shí)返回 true， 或者在失敗時(shí)返回 false。
示例 #1 mysqli::select_db() example
面向?qū)ο箫L(fēng)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();
?>
過(guò)程化風(fēng)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);
?>
以上例程會(huì)輸出：
Default database is test. Default database is world.