How to Efficiently Get Row Counts Using SELECT COUNT(*) in PHP?

*Use SELECT COUNT() efficiently in PHP to get the number of rows**

Direct SELECT all rows and then counting is inefficient. MySQL's SELECT COUNT(*) allows you to get the number of rows without retrieving the actual data.

Retrieve count value in PHP

To retrieve the count value from a SELECT COUNT(*) query, you cannot use $results->num_rows() as this method only works when selecting actual data. The following methods should be used:

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

Explanation of reasons

• Rename the result column to cnt to avoid conflict with MySQL reserved words.
• Use fetch_object() to get a single result object.
The
• result object's cnt property contains the count value.

How to use

if ($count) {
  // 表中存在行。
}

Other instructions

• SELECT COUNT(*) returns a table with only one row and one column, and the column name is cnt.
• Using fetch_row() or fetch_assoc() instead of fetch_object() will return an array with the count value at the first element.

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