PHP MySQL – 错误：未选择数据库

我正在尝试读取和写入数据库.这是我到目前为止的代码：

$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,它有一个错误：

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

谁能告诉我如何解决这个问题？

解决方法:

首先检查mysqli_select_db,如果它返回false,则创建数据库.

试试这样：

 $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：Php mysql create database if not exists

标签：create-table,php,mysql
来源： https://codeday.me/bug/20191003/1850463.html