MySQL inner join three tables to use in calendar - php

Question

Following up my question where I used the answer to generate data on my calendar called maintenance calendar showing the aircraft's maintenance schedule. This is the MySQL query for it:
SELECT DISTINCT s.reg AS 'reg',
a.date AS 'date'
FROM (SELECT Curdate()
+ INTERVAL (a.a + (10 * b.a) + (100 * c.a)) day AS Date
FROM (SELECT 0 AS a
UNION ALL SELECT 1
UNION ALL SELECT 2
UNION ALL SELECT 3
UNION ALL SELECT 4
UNION ALL SELECT 5
UNION ALL SELECT 6
UNION ALL SELECT 7
UNION ALL SELECT 8
UNION ALL SELECT 9) AS a
CROSS JOIN (SELECT 0 AS a
UNION ALL SELECT 1
UNION ALL SELECT 2
UNION ALL SELECT 3
UNION ALL SELECT 4
UNION ALL SELECT 5
UNION ALL SELECT 6
UNION ALL SELECT 7
UNION ALL SELECT 8
UNION ALL SELECT 9) AS b
CROSS JOIN (SELECT 0 AS a
UNION ALL SELECT 1
UNION ALL SELECT 2
UNION ALL SELECT 3
UNION ALL SELECT 4
UNION ALL SELECT 5
UNION ALL SELECT 6
UNION ALL SELECT 7
UNION ALL SELECT 8
UNION ALL SELECT 9) AS c) a
INNER JOIN maintenance_sched s
ON a.date >= s.date_from
AND a.date <= s.date_to
WHERE Month(date) = '".$month."'
AND Dayofmonth(date) = '".$dayArray["mday"]."'
AND Year(date) = '".$year."'
Here is the maintenance_sched database:
And the calendar looks like this (based on the data from maintenance_sched):
Then, I have another calendar called reservation calendar with the same code as the maintenance calendar though with different query. This is the reservation calendar query: SELECT acode FROM reservation WHERE month(etd) = '".$month."' AND dayofmonth(etd) = '".$dayArray["mday"]."' AND year(etd) = '".$year."' ORDER BY etd".
The reservation table is this:
And the reservation calendar looks like this:
EDIT:
What I want to do is: have these two calendar in one calendar with the result of maintenance_sched query outputted as string with strikethrough. But I can't seem to make the two queries work out together as one.

Answer 1

I do think the answer to this question is to simply join the two queries. An example of this might be like below where you just null out any columns that aren't in your second table.
SELECT id, date, field3, description
FROM table1
UNION
SELECT id, date, field3, null
FROM table2

Answer 2

As there is no relationship among both the table we cannot go for joins, it would be better to go for UNION to combine the result.
This query uses group_concat so will generate common results in following form
2013-03-15 | RP-C1728, RP-C1086
2013-03-08 | RP-C1728, RP-C1086, RP-C143
If you dont want record in this format then just remove group_concat, group by clause from the query.
Query
SELECT a.date, group_concat(a.reg)
FROM
(SELECT DISTINCT s.reg AS 'reg',
a.date AS 'date'
FROM (SELECT Curdate()
+ INTERVAL (a.a + (10 * b.a) + (100 * c.a)) day AS Date
FROM (SELECT 0 AS a
UNION ALL SELECT 1
UNION ALL SELECT 2
UNION ALL SELECT 3
UNION ALL SELECT 4
UNION ALL SELECT 5
UNION ALL SELECT 6
UNION ALL SELECT 7
UNION ALL SELECT 8
UNION ALL SELECT 9) AS a
CROSS JOIN (SELECT 0 AS a
UNION ALL SELECT 1
UNION ALL SELECT 2
UNION ALL SELECT 3
UNION ALL SELECT 4
UNION ALL SELECT 5
UNION ALL SELECT 6
UNION ALL SELECT 7
UNION ALL SELECT 8
UNION ALL SELECT 9) AS b
CROSS JOIN (SELECT 0 AS a
UNION ALL SELECT 1
UNION ALL SELECT 2
UNION ALL SELECT 3
UNION ALL SELECT 4
UNION ALL SELECT 5
UNION ALL SELECT 6
UNION ALL SELECT 7
UNION ALL SELECT 8
UNION ALL SELECT 9) AS c) a
INNER JOIN maintenance_sched s
ON a.date >= s.date_from
AND a.date <= s.date_to
WHERE Month(date) = '".$month."'
AND Dayofmonth(date) = '".$dayArray["mday"]."'
AND Year(date) = '".$year."'
UNION ALL
SELECT acode as 'reg', date as 'date' //Add the date logic here as per your need
FROM reservation
WHERE month(etd) = '".$month."' AND
dayofmonth(etd) = '".$dayArray["mday"]."' AND
year(etd) = '".$year."' ORDER BY etd) a
GROUP BY a.date;
NOTE For the second query add the according date logic