SELECT COUNT(*) AS count - 如何使用这个计数 [英] SELECT COUNT(*) AS count - How to use this count

问题描述

而不是这样做:

$cars = $mysqli->query("SELECT * FROM cars");
$count = $cars->num_rows();
if ($count) {
  // is rows
}

我不想选择所有行或单列，我只想要计数.

I want to not have to select all rows or a single column, I simply want the count.

在我的脑海中:

$cars = $mysqli->query("SELECT COUNT(*) as count FROM cars");

但是我该如何使用那个计数值呢?我需要对其运行 if 语句.

But then how do I use that count value? I need to run an if statement on it.

推荐答案

不建议在 SQL 中对名称使用保留字.所以我称计数结果为 cnt.由于您的函数是标量，即您只期望返回一个值，您可以使用:

It's not recommended to use reserved words for names in SQL. So I call the count result cnt instead. As your function is scalar, i.e. you expect only one value back, you can use:

$count = $mysqli->query("select count(*) as cnt from cars")->fetch_object()->cnt; 

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