如何判断列是否是使用 mysqli 的主键?

2021-12-25 00:00:00 php mysql mysqli primary-key

我正在将我的一些代码从旧的 mysql 扩展转换为 PHP 中的 mysqli 扩展.以前，使用mysql扩展，我曾使用过这样的代码来查找表中的主键:

I am converting some of my code from the older mysql extension to the mysqli extension in PHP. Previously, with the mysql extension, I had used some code like this to find the primary key in a table:

while ($i < mysql_num_fields($result)) {
    $meta = mysql_fetch_field($result, $i);
    if ($meta->primary_key == 1){ 
        $primary_key = $meta->name; 
    }
    $i++;
}

$meta->primary_key == 1 非常方便.

到目前为止，我已经转换为使用 mysqli 的代码:

So far I have converted to code to using mysqli:

while ($i < $result->field_count) {
    $meta = $result->fetch_field;
    if ($meta->primary_key == 1){ 
        $primary_key = $meta->name; 
    }
    $i++;
}

当然，通过查看文档这里我们可以看到 $meta->primary_key 在 mysqli 中不存在.我看到有一个 $meta->flags.这是我最好的猜测，虽然我不确定当我有主键时 flags 应该是什么值.

Of course, from looking at the docs here we can see that $meta->primary_key doesn't exist in mysqli. I see that there is a $meta->flags. This is my best guess, although i am not sure of what value flags should be when I have a primary key.

有谁知道我如何使用 mysqli 判断表的主键是哪一列?

Does anyone know how I tell which column is the primary key for a table using mysqli?

谢谢！

编辑这是一些工作代码:

//get primary key
$primary_key = '';
while ($meta = $result->fetch_field()) {
    if ($meta->flags & MYSQLI_PRI_KEY_FLAG) { 
        $primary_key = $meta->name; 
    }
}

推荐答案

您已经非常接近了，您将需要 flags 属性.

You were very close, you will need the flags property.

您正在寻找的标志是 MYSQLI_PRI_KEY_FLAG，意思是:

The flag you are looking for is MYSQLI_PRI_KEY_FLAG, which means:

字段是主索引的一部分

您可以使用以下内容测试此标志:

You can test for this flag with something like:

if ($meta->flags & MYSQLI_PRI_KEY_FLAG) { 
  //it is a primary key!
}

您在此处使用 & 作为 按位与运算符.

You are using & here as a Bitwise AND Operator.

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