PHP MySQL-错误:未选择数据库

问题描述：

我正在尝试读写数据库.这是我到目前为止的代码:

I am trying to read and write to a database. Here is the code I have so far:

$mysql = mysqli_connect("example.com", "johndoe", "abc123"); // replace with actual credidentials
$sql = "CREATE DATABASE IF NOT EXISTS dbname";
if (!mysqli_query($mysql, $sql)) {
    echo "Error creating database: " . mysqli_error($mysql);
}
if (mysqli_connect_errno()) {
    echo "Failed to connect to MySQL: " . mysqli_connect_error();
}
mysqli_close($mysql);
$mysql = mysqli_connect("example.com", "johndoe", "abc123", "dbname"); // replace with actual credidentials
$sql = "CREATE TABLE IF NOT EXISTS Users(ID INT NOT NULL AUTO_INCREMENT, PRIMARY KEY(ID), username CHAR(15), password CHAR(15), email CHAR(50))";
if (!mysqli_query($mysql, $sql)) {
    echo "Error creating table: " . mysqli_error($mysql);
}
$sql = "INSERT INTO Customers(username, password, email) VALUES(" . $username . ", " . $password . ", " . $email . ")";
if (!mysqli_query($mysql, $sql)) {
    echo "Error: " . mysqli_error($mysql);
}
mysqli_close($mysql);

但是，当我尝试运行它时，它出现了一个错误:

However, when I try to run it, it has an error:

Error: You have an error in your SQL syntax; check the manual that corresponds to your MySQL server version for the right syntax to use near ' , )' at line 1

有人可以告诉我如何解决此问题吗?

Could anybody tell me how to fix this?

答

首先检查mysqli_select_db是否返回false，然后创建数据库.

First check mysqli_select_db if it returns false then create database.

尝试这样:

 $mysql = mysqli_connect("example.com", "johndoe", "abc123") or die(mysqli_connect_error()); // replace with actual credidentials

if (!mysqli_select_db($mysql,'hardestgame_accounts')) {
 $sql = "CREATE DATABASE IF NOT EXISTS hardestgame_accounts";
 if (!mysqli_query($mysql, $sql)) {
    echo "Error creating database: " . mysqli_error($mysql);
 }
}
if (mysqli_connect_errno()) {
    echo "Failed to connect to MySQL: " . mysqli_connect_error();
}
$sql = "CREATE TABLE IF NOT EXISTS Users(ID INT NOT NULL AUTO_INCREMENT, PRIMARY KEY(ID), username CHAR(15), password CHAR(15), email CHAR(50))";
if (!mysqli_query($mysql, $sql)) {
    echo "Error creating table: " . mysqli_error($mysql);
}
mysqli_close($mysql);

这是一个很好的答案:如果没有的话，Php mysql创建数据库

here is a good answer: Php mysql create database if not exists

PHP MySQL-错误:未选择数据库

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