I'm developing a lawyer booking system, where a person can book an appointment at a given time in a given day (the next lawyer's available day).

Let's say it is a ZocDoc for lawyers. The same structure, with appointments based on time: https://www.zocdoc.com/search/?dr_specialty&address=San+Antonio,+TX&insurance_carrier=336&insurance_plan=2460&refine_search

I'm using MySQL and PHP.

The table schema:

CREATE TABLE `laywer_appointments` (
  `id` int(11) unsigned NOT NULL AUTO_INCREMENT,
  `lawyer_id` INT unsigned,
  `day_of_week` tinyint(3) unsigned DEFAULT '1',
  `slot_date` date DEFAULT NULL,
  `slot_time` time DEFAULT NULL,
  `status` tinyint(4) NOT NULL DEFAULT '0',
  `client_id` int(11) DEFAULT NULL, -- client_id = NULL means free slot
);

Point 1)

Each lawyer has default time slots based on the day of week (status = 0 means available). When inserting default slots, I don't provide a date, just day_of_week. Example data:

+-----------+-------------+-----------+-----------+
| lawyer_id | day_of_week | slot_time | status    |
+-----------+-------------+-----------+-----------+
| 1         | 1           | 08:00     | 0         |
| 1         | 1           | 08:30     | 0         |
| 1         | 1           | 09:00     | 0         |
| 1         | 1           | 10:30     | 0         |
| 1         | 4           | 14:30     | 0         |
| 1         | 4           | 16:40     | 0         |
| 2         | 1           | 10:20     | 0         |
| 2         | 1           | 14:00     | 0         |
| 2         | 3           | 15:50     | 0         |
+-----------+-------------+-----------+-----------+

Point 2)

A lawyer can add a time slot to a s