mysqli:为什么我需要一个if语句来创建一个表?-mysqli:WhydoIneeda'if'statementtocreateaTable?

I am learning MySQL with PHP and how to create tables & insert the Data. But I am particular confused about the following code:

我正在学习MySQL和PHP，以及如何创建表和插入数据。但我对下面的代码感到特别困惑:

//SECTION 1
$sql = "CREATE TABLE ingredients (
id INT(6) UNSIGNED AUTO_INCREMENT PRIMARY KEY,
quanity INT(6) NOT NULL,
package INT(6) NOT NULL,
item VARCHAR(50),
cost DECIMAL(18,2),
store VARCHAR(50),
reg_date TIMESTAMP
)";

//SECTION 2
if ($conn->query($sql) === TRUE) {
    echo "Table ingredients created successfully";
} else {
    echo "Error creating table: " . $conn->error;
}

//SECTION 3
$conn->close();

So I copied and pasted this code and ran it in my browser, then checked localhost/phpmyadmin and sure enough the TABLE was created.

因此，我复制并粘贴了这段代码并在浏览器中运行，然后检查localhost/phpmyadmin，并确保创建了表。

However, I then deleted the code and ran only SECTION 1, (section 2 & 3 were deleted and not present in the code) assuming this was all I needed to create a Table. After refreshing my browser, no Table in my Database was created.

但是，我随后删除了代码，只运行了第1部分(第2和第3部分被删除，并且没有出现在代码中)，假设这是创建表所需的全部内容。在刷新浏览器之后，我的数据库中没有创建任何表。

So I took another look and thought, its probably because I didn't close the connection. So this time I inserted SECTION 1 & SECTION 3 and left out SECTION 2.

所以我又看了一眼，心想，这可能是因为我没有关闭连接。所以这一次我插入了第1节和第3节，省略了第2节。

This also did not create a Table to my surprise. So this is where I am confused at. Why do I need SECTION 2? As far as I can tell from reading it, it only prints out a string, which is just a small notification to me or any user that a Table was created, but it doesn't seem vital in the making of a Table. Why then, can I NOT create a Table without it? I am confused!

这也没有创建一个表，让我吃惊。这就是我困惑的地方。为什么我需要第二部分?从我的阅读中可以看出，它只打印出一个字符串，对于我或任何用户来说，这只是一个创建表的小通知，但对于创建表来说，这似乎并不重要。那么，为什么我不能创建一个没有它的表呢?我是困惑!

2 个解决方案

//SECTION 1
$sql = "CREATE TABLE ingredients (
id INT(6) UNSIGNED AUTO_INCREMENT PRIMARY KEY,
quanity INT(6) NOT NULL,
package INT(6) NOT NULL,
item VARCHAR(50),
cost DECIMAL(18,2),
store VARCHAR(50),
reg_date TIMESTAMP
)";

//SECTION 2
if ($conn->query($sql) === TRUE) {
    echo "Table ingredients created successfully";
} else {
    echo "Error creating table: " . $conn->error;
}

//SECTION 2
$conn->query($sql);

//SECTION 3
$conn->close();