Question

I have 3 columns: Day, start_schedule and end_schedule.

   Day  |  start_schedule | end_schedule
 -------|-----------------|--------------
 Monday |     1:00        |   3:00
 Monday |     6:00        |   8:00
 Monday |     8:00        |  10:00

I’m still learning php. How will I filter if my input start schedule and end schedule is valid based on the stored times in the database?

For example if I want to add times

• start_schedule = 3:00 and end_schedule = 7:00

since there is 6:00 - 8:00 you shouldn’t be allowed to add this schedule.

• start_schedule = 7:00 and end_schedule = 11:00

since there are 6:00 - 8:00 and 8:00 - 10:00 you shouldn’t be allowed to add this schedule.

Answer 1

I would do most of the logic in mysql since it will handle these kinds of expressions very easy and straight forward approaches.

In PHP, before inserting a new entry we will need to check 1 thing:

1. Is end_time less than start_time? If so, abort.

In MySQL, when trying to insert a new entry we will need to check 4 things:

1. Is the start_time inside any existent entry? If so, abort.
2. Is the end_time inside any existent entry? If so, abort.
3. Is there any entry starting that would be inside our new entry? If so, abort.
4. Is there any entry ending that would be inside our new entry? If so, abort.

The above can actually be refactored into one steps:

1. Is there our start time less than any entries end time, AND is our end time larger than that entires start time? If so, abort.

---

mysql> describe sample;
+-------+-------------+------+-----+---------+-------+
| Field | Type        | Null | Key | Default | Extra |
+-------+-------------+------+-----+---------+-------+
| start | time        | YES  |     | NULL    |       |
| end   | time        | YES  |     | NULL    |       |
| day   | varchar(50) | YES  |     | Monday  |       |
+-------+-------------+------+-----+---------+-------+

mysql> SELECT * FROM sample;
+--------+----------+----------+
| day    | start    | end      |
+--------+----------+----------+
| Monday | 01:00:00 | 03:00:00 |
| Monday | 06:00:00 | 08:00:00 |
| Monday | 08:00:00 | 11:00:00 |
+--------+----------+----------+

---

Sample implementation in PHP querying the database:

Props to @regilero for posting a re-factored version of the where claus required.

$new_entries = array (
  array('Monday', '00:00:00', '23:59:00'),
  array('Monday', '12:00:00', '15:00:00'),
  array('Monday', '07:00:00', '10:00:00')
);

foreach ($new_entries as $new) {
  list ($day, $start, $end) = $new;

  $q_day   = "'$day'";
  $q_end   = "'$end'";
  $q_start = "'$start'";

  $sql = <<<EOQ
    INSERT INTO `sample` (day,start,end)
    SELECT $q_day, $q_start, $q_end FROM DUAL
    WHERE NOT EXISTS (
      SELECT * FROM `sample`
      WHERE day = $q_day AND (
        $q_start < end AND $q_end > start
      )
    )
EOQ;

  mysql_query ($sql) or die (mysql_error ());

  if (mysql_affected_rows () == 0)
    print join (' ', $new) . " was not inserted!\n";
  else
    print join (' ', $new) . " was inserted!\n";
}

This would output:

Monday 00:00:00 23:59:00 was not inserted!
Monday 12:00:00 15:00:00 was inserted!
Monday 07:00:00 10:00:00 was not inserted!