如何在 PHP 中使用 mysqli_query()? [英] How to use mysqli_query() in PHP?

问题描述

我正在用 PHP 编码.我有以下 mySQL 表:

I'm coding in PHP. I have the following mySQL table:

CREATE TABLE `students` (
  `ID` int(10) NOT NULL AUTO_INCREMENT,
  `Name` varchar(255) DEFAULT NULL,
  `Start` int(10) DEFAULT NULL,
  `End` int(10) DEFAULT NULL,
   PRIMARY KEY (`ID`)
 ) ENGINE=InnoDB;

我正在尝试使用 PHP 中的 mysqli_query 函数来描述表.

I'm trying to use the mysqli_query function in PHP to DESCRIBE the table.

这是我的代码:

$link = mysqli_connect($DB_HOST, $DB_USER, $DB_PASS, $DATABASE);
$result = mysqli_query($link,"DESCRIBE students");

文档说对于成功的 SELECT、SHOW、DESCRIBE 或 EXPLAIN 查询，mysqli_query() 将返回 mysqli_result 对象.

The documentation says For successful SELECT, SHOW, DESCRIBE or EXPLAIN queries mysqli_query() will return a mysqli_result object.

但是从那里我不知道如何打印 $result 以便它显示查询结果.如果可能，我想打印 $result 使其看起来像:

But from there I don't know how to print $result so that it shows the query results. If possible I want to print $result so that it looks like:

+----------+--------------+------+-----+---------+----------------+
| Field    | Type         | Null | Key | Default | Extra          |
+----------+--------------+------+-----+---------+----------------+
| ID       | int(10)      | NO   | PRI | NULL    | auto_increment |
| Name     | varchar(255) | YES  |     | NULL    |                |
| Start    | int(10)      | YES  |     | NULL    |                |
| End      | int(10)      | YES  |     | NULL    |                |
+----------+--------------+------+-----+---------+----------------+ 

我的另一个问题是如何打印查询SHOW CREATE TABLE Students.

My other question is how to print the query SHOW CREATE TABLE students.

$result = mysqli_query($link,"SHOW CREATE TABLE students");

推荐答案

我不得不承认，mysqli_query() 手册条目没有包含关于如何获取多行的清晰示例.可能是因为套路太套路了，PHP 人都知道几十年了:

I have to admit, mysqli_query() manual entry doesn't contain a clean example on how to fetch multiple rows. May be it's because the routine is so routine, known to PHP folks for decades:

$result = $link->query("DESCRIBE students");
while ($row = $result->fetch_assoc()) {
    // to print all columns automatically:
    foreach ($row as $value) {
        echo "<td>$value</td>";
        // OR to print each column separately:
        echo "<td>",$row['Field'],"</td><td>",$row['Type'],"</td>
";
    }
}

如果要打印列标题，必须先将数据选入嵌套数组，然后使用第一行的键:

In case you want to print the column titles, you have to select your data into a nested array first and then use keys of the first row:

// getting all the rows from the query
// note that handy feature of OOP syntax
$data = $link->query("DESC students")->fetch_all(MYSQLI_ASSOC);
// getting keys from the first row
$header = array_keys(reset($data));
// printing them
foreach ($header as $value) {
    echo "<td>$value</td>";
}
// finally printing the data
foreach ($data as $row) {
    foreach ($row as $value) {
        echo "<td>$value</td>";
    }
}

某些主机可能不支持 fetch_all() 函数.在这种情况下，按照通常的方式填充 $data 数组:

Some hosts may have no support for the fetch_all() function. In such a case, fill the $data array the usual way:

$data = [];
$result = $link->query("DESC students");
while ($row = $result->fetch_assoc())
{
    $data[] = $row;
}

我必须补充两个重要的说明.

1. 您必须将 mysqli 配置为自动抛出错误，而不是手动检查每个 mysqli 语句的错误.为此，在 before mysqli_connect() 之前添加这一行:

 mysqli_report(MYSQLI_REPORT_ERROR | MYSQLI_REPORT_STRICT);

最重要的提示:与mysql_query()不同，mysqli_query()的用途非常有限.仅当查询中不使用任何变量时，您才可以使用此函数.如果要使用任何 PHP 变量，则永远不要使用 mysqli_query()，但始终坚持准备好的声明，如下所示:

The most important note: unlike mysql_query(), mysqli_query() has a very limited use. You may use this function only if no variables are going to be used in the query. If any PHP variable is going to be used, you should never use mysqli_query(), but always stick to prepared statements, like this:

 $stmt = $mysqli->prepare("SELECT * FROM students WHERE class=?");
 $stmt->bind_param('i', $class);
 $stmt->execute();
 $data = $stmt->get_result()->fetch_all();

这有点罗嗦，我不得不承认.为了减少代码量，您可以使用 PDO 或采用简单的辅助函数来完成所有工作里面的准备/绑定/执行业务:

It's a bit wordy, I have to admit. In order to reduce the amount of code you can either use PDO or adopt a simple helper function to do all the prepare/bind/execute business inside:

$sql = "SELECT * FROM students WHERE class=?";
$data = prepared_select($mysqli, $sql, [$class])->fetch_all();

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