Summarize some knowledge points of vue3: MySQL chooses database

Table of contents

MySQL select database

Select the MySQL database from the command prompt window

example

Select MySQL database using PHP script

grammar

example

select database

---

After you connect to the MySQL database, there may be multiple databases that can be operated, so you need to select the database you want to operate.

---

Select the MySQL database from the command prompt window

A specific database can be easily selected in the mysql> prompt window. You can use SQL commands to select specific databases.

example

The following example selects the database RUNOOB:

[root@host]# mysql -u root -p
Enter password:******
mysql> use RUNOOB;
Database changed
mysql>

After executing the above command, you have successfully selected the RUNOOB database, and all subsequent operations will be executed in the RUNOOB database.

---

Select MySQL database using PHP script

PHP provides the function mysqli_select_db to select a database. The function returns TRUE if executed successfully, otherwise returns FALSE.

grammar

mysqli_select_db(connection,dbname);

parameter	describe
connection	required. Specifies the MySQL connection to use.
dbname	Required, specifies the default database to use.

example

The following example shows how to use the mysqli_select_db function to select a database:

select database

<?php
$dbhost = 'localhost';  // mysql服务器主机地址
$dbuser = 'root';            // mysql用户名
$dbpass = '123456';          // mysql用户名密码
$conn = mysqli_connect($dbhost, $dbuser, $dbpass);
if(! $conn )
{
    die('连接失败: ' . mysqli_error($conn));
}
echo '连接成功';
mysqli_select_db($conn, 'RUNOOB' );
mysqli_close($conn);
?>