MYSQL comparing time and day of week simultaneously

Question

I have the following table in MYSQL database.

CREATE TABLE IF NOT EXISTS `wp_my_default_settings` (
  `ds_id` int(11) NOT NULL AUTO_INCREMENT,
  `user_id` int(11) NOT NULL,
  `whichday` varchar(10) NOT NULL,
  `tillday` varchar(10) NOT NULL,
  `start_time` varchar(10) NOT NULL,
  `end_time` varchar(10) NOT NULL,
  `max_no_msg` int(11) NOT NULL,
  `created_date` datetime NOT NULL,
  PRIMARY KEY (`ds_id`)
) ENGINE=MyISAM  DEFAULT CHARSET=latin1 AUTO_INCREMENT=11 ;

--
-- Dumping data for table `wp_my_default_settings`
--

INSERT INTO `wp_my_default_settings` (`ds_id`, `user_id`, `whichday`,         `tillday`, `start_time`, `end_time`, `max_no_msg`, `created_date`) VALUES
(10, 11, 'Thu', 'Fri', '11:57 PM', '01:54 PM', 22, '2015-06-05 13:56:04'),
(9, 11, 'Thu', 'Thu', '12:06 AM', '02:46 PM', 20, '2015-06-05 13:56:04'),
(8, 11, 'Wed', 'Wed', '05:11 AM', '12:47 PM', 34, '2015-06-05 13:56:04'),
(7, 11, 'Tue', 'Tue', '10:02 AM', '05:14 PM', 50, '2015-06-05 13:56:04'),
(6, 11, 'Sun', 'Sun', '06:30 PM', '06:30 PM', 40, '2015-06-05 13:56:04');

I have a time specified as Fri 7:16 AM

I want to formulate a query selecting that row which has 'Fri 7:16' BETWEEN CONCAT( CONCAT( whichday, ' ' ) , start_time ) AND CONCAT( CONCAT( tillday, ' ' ) , end_time )
My query is

   SELECT `ds_id` , `whichday` , `start_time` , `tillday` ,    
`end_time` , STR_TO_DATE( CONCAT( CONCAT( whichday, ' ' ) , start_time ) , '%a %h:%i %p' ) AS 'Start', 
    STR_TO_DATE( CONCAT( CONCAT( tillday, ' ' ) , end_time ) , '%a %h:%i %p' ) AS 'End', 
    STR_TO_DATE( 'Fri 07:16 AM', '%a %h:%i %p' ) AS 'Current' 
    FROM `wp_my_default_settings`
    WHERE `user_id` = '11'
    AND (
        STR_TO_DATE( 'Fri 07:16 AM', '%a %h:%i %p' )
        BETWEEN STR_TO_DATE( CONCAT( CONCAT( whichday, ' ' ) , start_time ) , '%a %h:%i %p' )
        AND STR_TO_DATE( CONCAT( CONCAT( tillday, ' ' ) , end_time ) , '%a %h:%i %p'         )
    )    
    AND `max_no_msg` >= (
    SELECT COUNT( `offer_id` )
    FROM `wp_user_offers_by_adv`
    WHERE `offer_user_id` = '11' )

Instead of getting row with ds_id=10 I get rows with ds_id 8 and 9

Please help

Answer 1

The problem is, that STR_TO_DATE( 'Fri 07:16 AM', '%a %h:%i %p' ) results in 0000-00-00 07:16:00 and this happens to all your "dates". This means you loose the day-of-the-week information.

You can fix this by replacing the day of the week by a date. E.g. You can use 2015-06-01 as Monday and 2015-06-07 as Sunday.

But there are a lot to improve in the whole table structure.

• Store the times in a TIME field.
  This saves you about 6 bytes (or 66%) per field and can make queries easier.

• Store the day-of-the-week as a number (1 to 7) in a TINYINT field.
  This saves you about 3 bytes (or 75%) and enables you to make the query like this:

  ... WHERE (whichday < input_day 
              OR whichday = input_day AND start_time <= input_time))
            AND
            (tillday > input_day 
              OR tillday = input_day AND end_time >= input_time)))
  

  No more need for CONCAT and STR_TO_DATE which means you can use indexes better.

• Alternative to the first two point you can store the day and the time in a DATETIME field, using a date, that has the right day-of-the-week. If you put all your dates in the same week (e.g. the week from 2015-06-01 to 2015-06-07) you can make queries just like

  ... WHERE input_date BETWEEN start_datetime AND end_datetime