定義和用法
這個mysqli_select_db()函數接受一個表示現有數據庫的字符串值,並將其作為默認數據庫。
用法
mysqli_select_db($con, name)
參數
Sr.No | 參數及說明 |
---|---|
1 |
con(Mandatory) 這是一個表示與 MySQL 服務器的連接的對象。 |
2 |
name(Mandatory) 這是一個字符串值,表示您需要將其設為默認數據庫的現有數據庫的名稱。 |
返回值
PHP mysqli_select_db() 函數返回一個布爾值,如果操作成功則為真,否則為假。
PHP版本
這個函數最初是在 PHP 版本 5 中引入的,適用於所有後續版本。
示例
以下示例演示了 mysqli_select_db() 函數的用法(程序風格) -
<?php
//Creating a connection
$con = mysqli_connect("localhost", "root", "password", "mydb");
//Selecting the database
mysqli_query($con, "CREATE DATABASE NewDatabase");
mysqli_select_db($con, "NewDatabase");
//Retrieving the current database name
$res = mysqli_query($con, "SELECT DATABASE()");
while ($row = mysqli_fetch_row($res)) {
print("Current Database:".$row[0]);
}
//Closing the connection
mysqli_close($con);
?>
這將產生以下結果 -
Current Database:newdatabase
示例
在麵向對象的風格中,這個函數的語法是 $con->select_db();以下是麵向對象樣式 $minus 中此函數的示例;
<?php
//Creating a connection
$con = new mysqli("localhost", "root", "password", "mydb");
//Retrieving the current database name
$res = $con->query("SELECT DATABASE()");
while ($row = $res->fetch_row()) {
print("Initial Database:".$row[0]."\n");
}
//Selecting the database
$con->query("CREATE DATABASE NewDatabase");
$con->select_db("NewDatabase");
//Retrieving the current database name
$res = $con->query("SELECT DATABASE()");
while ($row = $res->fetch_row()) {
print("Current Database:".$row[0]);
}
//Closing the connection
$res = $con -> close();
?>
這將產生以下結果 -
Initial Database:mydb Current Database:newdatabase
示例
除了在連接時指定數據庫,您也可以稍後使用此函數選擇它,如下所示 -
<?php
//Creating a connection
$con = mysqli_connect("localhost", "root", "password");
//Selecting the database
mysqli_select_db($con, "mydb");
print("Database Selected ..."."\n");
mysqli_query($con, "CREATE TABLE IF NOT EXISTS my_team(ID INT, First_Name VARCHAR(255), Last_Name VARCHAR(255), Place_Of_Birth VARCHAR(255), Country VARCHAR(255))");
print("Table Created ..."."\n");
//Inserting a records into the my_team table
mysqli_query($con, "insert into my_team values(1, 'Shikhar', 'Dhawan', 'Delhi', 'India')");
mysqli_query($con, "insert into my_team values(2, 'Jonathan', 'Trott', 'CapeTown', 'SouthAfrica')");
mysqli_query($con, "insert into my_team values(3, 'Kumara', 'Sangakkara', 'Matale', 'Srilanka')");
mysqli_query($con, "insert into my_team values(4, 'Virat', 'Kohli', 'Delhi', 'India')");
print("Records Inserted ..."."\n");
//Closing the connection
mysqli_close($con);
?>
這將產生以下結果 -
Database Selected ... Table Created ... Records Inserted ...
示例
<?php
$connection_mysql = mysqli_connect("localhost", "root", "password","mydb");
if (mysqli_connect_errno($connection_mysql)){
echo "Failed to connect to MySQL:" . mysqli_connect_error();
}
$res = mysqli_select_db($connection_mysql,"testdb");
if($res){
echo "Database Selected";
}else{
echo "Error Occurred";
}
mysqli_close($connection_mysql);
?>
這將產生以下結果 -
Database Selected
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