问题描述
在一个场景中，我需要知道查询将返回的记录集计数，这在 codeigniter 中可以通过 $query->num_rows() 或 $this-> 来完成；db->count_all_results().哪个更好，这两个有什么区别?
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?
推荐答案
使用 num_rows() 你首先执行查询，然后你可以检查你得到了多少行.count_all_results() 另一方面，只给你查询将产生的行数，但不给你实际的结果集.
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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