SELECT COUNT(*) AS count - 如何使用此计数

SELECT COUNT(*) AS count - How to use this count(SELECT COUNT(*) AS count - 如何使用此计数)

问题描述

Instead of doing:

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

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

In my head:

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

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

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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