In mysql how to select columns in a union join - mysql

Question

How to select join table's columns when I'm using union. Specifically how to select b.id(booking id) in the following query? Also is it the right way to do it? Can you please tell me any other way to do it? I also want to select available time for a selected date if any available. I have three categories of timing.
cat1(category 1): availability on particular days of week(Example:Mon, Tue, Wed, etc of any month)
cat2(category 2): availability on First monday, second saturday, etc of any months.
cat3(category 3): availability on last saturday, last friday, etc of
any month.
I'm using day_offset, and cat columns in my doctor_schedule table to calculate date and checking it to #selected_date. I am also filtering off days with the help of my off_day table (off_days table stores information for any holidays, or if doctor taking leave for any personal reasons).
mysql> select * from doctor;
+----+-------------+
| id | name |
+----+-------------+
| 1 | John Doe |
| 2 | Larry Jones |
+----+-------------+
mysql> select * from doctor_schedule;
+----+-----------+-----+------------+----------+---------------+--------+------------+-----+
| id | doctor_id | day | start_time | end_time | booking_limit | active | day_offset | cat |
+----+-----------+-----+------------+----------+---------------+--------+------------+-----+
| 1 | 2 | 5 | 10:00:00 | 12:00:00 | 1 | 1 | 3 | 2 |
| 2 | 2 | 5 | 19:00:00 | 22:00:00 | 1 | 1 | 3 | 2 |
| 3 | 2 | 6 | 19:00:00 | 22:00:00 | 1 | 1 | 0 | 3 |
+----+-----------+-----+------------+----------+---------------+--------+------------+-----+
mysql> select * from booking;
+----+---------+-------------+--------------+------+
| id | user_id | schedule_id | booking_date | paid |
+----+---------+-------------+--------------+------+
| 1 | 1 | 3 | 2017-06-26 | 1 |
+----+---------+-------------+--------------+------+
mysql> select * from off_day;
+----+-----------+-------------+------------+
| id | doctor_id | schedule_id | date |
+----+-----------+-------------+------------+
| 2 | 1 | 3 | 2017-06-26 |
+----+-----------+-------------+------------+
set #selected_date := "2017-06-26";
set #doctor_id := 2;
SET #first_day = DATE_SUB(#selected_date, INTERVAL DAYOFMONTH(#selected_date) - 1 DAY);
select s.*
from
(select
s1.id
from doctor_schedule s1
where
s1.cat = 1
and
s1.day = weekday(#selected_date)
UNION
select
s2.id
from doctor_schedule s2
where
s2.cat = 2
and
DATE_ADD(#first_day, INTERVAL (s2.day - WEEKDAY(#first_day)) + (s2.other*7) DAY) = #selected_date
UNION
select
s3.id
from doctor_schedule s3
where
s3.cat = 3
and
date_sub(LAST_DAY(#selected_date), INTERVAL ((7 + WEEKDAY(LAST_DAY(#selected_date)) - s3.other) % 7) DAY) = #selected_date
) as s
right join
booking b
on
s.id = b.schedule_id
and
b.booking_date >= #selected_date
and
b.paid = 1
left join
off_day o
on
s.id = o.schedule_id
and
o.date = #selected_date
and
o.doctor_id = #doctor_id
where
o.schedule_id is null
group by
s.id

Answer 1

Mr. Tim Biegeleisen pointed that there is no booking_id in my query. Thanks to him that I found the solution. It should be b.id.
set #selected_date := "2017-06-26";
set #doctor_id := 2;
SET #first_day = DATE_SUB(#selected_date, INTERVAL
DAYOFMONTH(#selected_date) - 1 DAY);
select s.*, b.id
from
(select
s1.id
from doctor_schedule s1
where
s1.cat = 1
and
s1.day = weekday(#selected_date)
UNION
select
s2.id
from doctor_schedule s2
where
s2.cat = 2
and
DATE_ADD(#first_day, INTERVAL (s2.day - WEEKDAY(#first_day)) + (s2.other*7) DAY) = #selected_date
UNION
select
s3.id
from doctor_schedule s3
where
s3.cat = 3
and
date_sub(LAST_DAY(#selected_date), INTERVAL ((7 + WEEKDAY(LAST_DAY(#selected_date)) - s3.other) % 7) DAY) = #selected_date
) as s
right join
booking b
on
s.id = b.schedule_id
and
b.booking_date >= #selected_date
and
b.paid = 1
left join
off_day o
on
s.id = o.schedule_id
and
o.date = #selected_date
and
o.doctor_id = #doctor_id
where
o.schedule_id is null
group by
s.id