Re: {CodeIgniter Kenya} Digest for codeigniter-kenya@googlegroups.com - 2 Messages in 1 Topic

[Nd'wex Common]

If my memory serves me right if the query fails due to some error there will be an error message and it "halts" whereas in the event there no records num_rows() returns false/0.

$rs = $this->db->query(some query here);
if($rs->num_rows() > 0)
{
   $rs = $rs->result();   //returns an array of objects
   foreach($rs as $objects)
   {
      //do something with the data here
   }

   return $something;
}

return FALSE;

On Sat, Aug 3, 2013 at 10:19 AM, <codeigni...@googlegroups.com> wrote:

  Today's Topic Summary

Group: http://groups.google.com/group/codeigniter-kenya/topics

• PHP/MySQL: Is there a better way to count distinct values in a column [2 Updates]

 PHP/MySQL: Is there a better way to count distinct values in a column

Isaak Mogetutu <imog...@gmail.com> Aug 02 12:34AM -0700  

I'm eeked out by this code segment:
 
if ($result == FALSE) {
return FALSE;
}

if ($result->num_rows() == 0) {
return FALSE;
}
 
Quick question if $result == false can $result->num_rows() != 0 thats why
the double checks for false
Instead can you check if its true load master array else return false
 
// Not tested just my thoughts
function count_distinct_values($table_name = '', $column_name = '')
{
$result = $this->db->query("SELECT $column_name, count(*) AS
value_count FROM $table_name GROUP BY $column_name");

if ($result) {
$master_array = array();
foreach ($result->result_array() as $row) {
$master_array[$row[$column_name]] = $row['value_count'];
}

return $master_array;
}

return FALSE;
}
 
 
 
On Thursday, 1 August 2013 16:49:14 UTC+3, Peter Karunyu wrote:


 

Peter Karunyu <pkar...@gmail.com> Aug 02 10:39AM +0300  

I got into the habit of separating num_rows() from the other one coz I
sometimes need to differentiate from a query failing (which is super bad)
to a query not returning any data (which is ok).
 
But in the example above, there's no need for that so yes, your suggestion
is better
 
 
 
--
Regards,
Peter Karunyu
-------------------


 

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[Peter Karunyu]

Using the world database, I have run this query which should return 209 rows:
$rs = $this->db->query("SELECT * FROM country");

And var_dump($rs) gives:
object(CI_DB_mysql_result)#14 (8) { ["conn_id"]=> resource(7) of type (mysql link persistent) ["result_id"]=> resource(8) of type (mysql result) ["result_array"]=> array(0) { } ["result_object"]=> array(0) { } ["custom_result_object"]=> array(0) { } ["current_row"]=> int(0) ["num_rows"]=> int(239) ["row_data"]=> NULL }

Now, if I run this query which should return zero results:
$rs = $this->db->query("SELECT * FROM country WHERE CODE='ABC'");

var_dump($rs) gives:
object(CI_DB_mysql_result)#14 (8) { ["conn_id"]=> resource(6) of type (mysql link persistent) ["result_id"]=> resource(7) of type (mysql result) ["result_array"]=> array(0) { } ["result_object"]=> array(0) { } ["custom_result_object"]=> array(0) { } ["current_row"]=> int(0) ["num_rows"]=> int(0) ["row_data"]=> NULL } 

So, i think a query that returns no results does NOT return false, it returns the same object a successful query does, only that the sub-objects i.e. $rs->result(), do not have any data.

If I run this erroneous query:
$rs = $this->db->query("SELECT * FROM non_existent_table");

CI throws a database error such as:
A Database Error Occurred
Error Number: 1146
Table 'world.non_existent_table' doesn't exist
SELECT * FROM non_existent_table
Filename: /Users/Peter/Sites/ci_test/controllers/welcome.php
Line Number: 22

Now, in a production environment, I don't want to be showing such a descriptive error to users, I want to show a different error message, AND log the occurrence of that said to the log files, and possibly send myself an email.

To achieve this:
1. The ENVIRONMENT in index.php will be set to PRODUCTION
2. In config/database.php, $db['default']['db_debug'] = TRUE; will be set to FALSE.

3. In config/config.php, $config['log_threshold'] = 0; will be set to at least 1.

Therefore, modifying your code slightly, I end up with this:

$rs = $this->db->query("SELECT * FROM non_existent_table");

if ($rs == FALSE) {
    log_message('error', "DB Error: (".$this->db->_error_number().") ".$this->db->_error_message(). ' Path: '.$this->uri->uri_string());
    show_error('Sorry, a database error occurred, Tech Support has been notified. Please try again later.');
    return FALSE;

}

if($rs->num_rows() > 0)
{
    $rs = $rs->result();   //returns an array of objects
   
    foreach($rs as $objects)
    {
        //do something with the data here
    }

    return $something;
}

return FALSE;