CodeIgniter 中的 $query>num_rows() 和 $this->db->count_all_results() 之间的区别 & 推荐哪一个

Question

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?

Answer 1

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

Answer 2

$this->db->count_all_results is part of an Active Record query (preparing the query, to only return the number, not the actual results).

$query->num_rows() is performed on a resultset object (after returning results from the DB).

Answer 3

Which one is better and what is the difference between these two Its almost imposibble to me, someone just want to get the number of records without re-touching or perform another query which involved same resource. Furthermore, the memory used by these two function is in same way after all, since with count_all_result you still performing get (in CI AR terms), so i recomend you using the other one (or use count() instead) which gave you reusability benefits.

Answer 4

There are two ways to count total number of records that the query will return. First this

$query = $this->db->query('select blah blah');  
return $query->num_rows();

This will return number of rows the query brought.

Second

return $this->db->count_all_results('select blah blah');

Simply count_all_results will require to run the query again.

Answer 5

We can also use

return $this->db->count_all('table_name');  

or

$this->db->from('table_name');
return $this->db->count_all_result();

or

return $this->db->count_all_result('table_name');

or

$query = $this->db->query('select * from tab');  
return $query->num_rows();

Answer 6

Total number of results

$this->db->count_all_results('table name');

Answer 7

Simply as bellow;

$this->db->get('table_name')->num_rows();

This will get number of rows/records. however you can use search parameters as well;

$this->db->select('col1','col2')->where('col'=>'crieterion')->get('table_name')->num_rows();

However, it should be noted that you will see bad bad errors if applying as below;

$this->db->get('table_name')->result()->num_rows();

Answer 8

$sql = "select count(*) as row from login WHERE firstname = '" . $username . "' AND password = '" . $password . "'";
    $query = $this->db->query($sql);
    print_r($query);exit;
    if ($query->num_rows() == 1) {
    return true;
    } else {
    return false;
    }