MYSQL date range query strange behaviour - php

Question

i'm working on codeigniter and mysql db. I have run in to a issue where i need to show recent data as per date.
i have table name tbl_tournament where i'm going to fetch tournament data whose tournament_end_date >= $todays_date
My Query
$today = date("d/m/Y");
$this->db->select('*');
$this->db->from('tbl_tournament');
$this->db->where('is_deleted', FALSE);
$this->db->where('tournament_end_date_time >=', $today);
$this->db->order_by('tournament_start_date_time');
$query = $this->db->get();
return $query->result_array();
the output of this query is empty array
array();
When i manually change tournament_end_date_time = 01/04/2018 in database and query $this->db->where('tournament_end_date_time >=', '01/04/2017'); i get results. But when i change date in query as $this->db->where('tournament_end_date_time >=', '31/12/2017'); i get empty array.
In Mysql database i have used varchar as the data type tournament_end_date_time
Thank in Advance.

Answer 1

You store datetimes as strings (with VARCHAR type), hence they're compared as strings - character by character. For obvious reasons, '3' character is greater than '1'. That's why with filter set...
WHERE tournament_end_date_time >= '31/12/2017'
... you'll only get the results where corresponding values start from '31/12' - in other words, of December, 31 (of 2017 - or any year after it).
To solve the problem, you can use STR_TO_DATE() MySQL function to convert the existing column value to an actual date. Note that the param will be treated as a date literal as it follows 'YYYY-MM-DD' format:
WHERE STR_TO_DATE(tournament_end_date_time, '%d/%m/%Y') >= '2017-12-31'
... or, in PHP syntax, following CodeIgniter conventions:
$this->db->where(array(
"STR_TO_DATE(tournament_end_date_time, '%d/%m/%Y') >=" => date("Y-m-d")
));
A better choice is doing a single-time update operation on this column to convert all its values to DATE type at once.