CodeIgniter& C中的$ query> num_rows（）和$ this-> db-> count_all_results（）建议一个 [英] difference between $query>num_rows() and $this->db->count_all_results() in CodeIgniter & which one is recommended

问题描述

在一个场景中，我需要知道查询将返回的记录集的计数，在codeigniter中可以通过 $ query-> num_rows（）或 $ this-> db-> count_all_results（）。 code>你首先执行查询，然后你可以检查你有多少行。 count_all_results（）另一方面只给出查询会产生的行数，但不会给出实际的结果集。

  // num rows example 
 $ this-> db-> select（'*'）; 
 $ this-> db-> where（'whatever'）; 
 $ query = $ this-> db-> get（'table'）; 
 $ num = $ query-> num_rows（）; 
 //这里你可以用$ query 
 
做一些事情// count all example 
 $ this-> db-> where（'whatever'）; 
 $ num = $ this-> db-> count_all_results（'table'）; 
 //这里你只有$ num，没有$ query 
  

In a scenario I need to know the count of recordset a query will return, which in codeigniter can be done by $query->num_rows() or $this->db->count_all_results(). Which one is better and what is the difference between these two?

解决方案

With num_rows() you first perform the query, and then you can check how many rows you got. count_all_results() on the other hand only gives you the number of rows your query would produce, but doesn't give you the actual resultset.

// num rows example
$this->db->select('*');
$this->db->where('whatever');
$query = $this->db->get('table');
$num = $query->num_rows();
// here you can do something with $query

// count all example
$this->db->where('whatever');
$num = $this->db->count_all_results('table');
// here you only have $num, no $query

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