Mysql, Show who has and hasn't opted out of bus service - mysql

Question

I have student and event tables linked by sid.
CREATE TABLE `students` (
`sid` int(8) NOT NULL COMMENT 'use',
`active` enum('Yes','No','vac','Grad') NOT NULL DEFAULT 'Yes',
`name` varchar(130) DEFAULT NULL,
`bus` varchar(130) DEFAULT NULL
) ENGINE=MyISAM DEFAULT CHARSET=utf8;
INSERT INTO `students` (`sid`, `LEFT(name, 2)`, `bus`) VALUES
(51, 'Me', 'BusA'),
(52, 'Hi', 'BusA'),
(59, 'An', 'BusA'),
(70, 'Mi', 'BusB'),
(100, 'Yu', 'BusB');
CREATE TABLE `STATevent` (
`eventid` int(24) NOT NULL,
`sid` int(4) NOT NULL,
`date` datetime NOT NULL,
`created` timestamp NOT NULL DEFAULT CURRENT_TIMESTAMP,
`level` enum('absent','bus') CHARACTER SET utf8 NOT NULL,
`color` varchar(10) NOT NULL,
`Percent` tinyint(5) NOT NULL,
`note` varchar(266) NOT NULL
) ENGINE=MyISAM DEFAULT CHARSET=utf8;
INSERT INTO `STATevent` (`eventid`, `sid`, `date`, `created`, `level`, `color`, `Percent`, `note`) VALUES
(43, 59, '2022-11-30 21:17:04', '2022-11-28 12:17:04', 'bus', 'red', 100, '');
The student can select not to get bus service, which shows as an entry (like eventid 43 above). I can get the list of 'bus students', along with an id to show who cancelled service and who hasn't.
SELECT C.name, C.sid, O.sid AS 'bid', C.bus FROM students C
LEFT JOIN STATevent O ON C.sid = O.sid
WHERE C.bus LIKE 'Bus%' AND C.active = 'Yes' ;
However, when I try to limit where with the date, the result shows only the one who cancelled service.
SELECT C.name, C.sid, O.sid AS 'bid', C.bus FROM students C
LEFT JOIN STATevent O ON C.sid = O.sid
WHERE C.bus LIKE 'Bus%' AND C.active = 'Yes' AND O.date LIKE '2022-11-29%';
How can I add this limiter and get the full results like the first query?
Thanks in advance for your help.

Answer 1

You may move the restriction on the event date to the ON clause of the left join:
SELECT c.name, c.sid, o.sid AS bid, c.bus
FROM students c
LEFT JOIN STATevent o
ON o.sid = c.sid AND
DATE(o.date) = '2022-11-29'
WHERE c.bus LIKE 'Bus%' AND c.active = 'Yes';
For students who did not cancel service, the bid would be reported as null.

Answer 2

You want to show all students that use a bus servvice, but exclude those that opt out for a certain date. You can use NOT EXISTS or NOT IN to do this lookup.
SELECT *
FROM `students`
WHERE bus LIKE 'Bus%' AND active = 'Yes'
AND sid NOT IN
(
SELECT sid
FROM `STATevent`
WHERE DATE(date) = DATE '2022-11-30'
)
ORDER BY sid;
If you want to show all potential bus service users instead with a flag whether they attend that day or not, you can move the condition to the select clause:
SELECT s.*
sid IN
(
SELECT sid
FROM `STATevent`
WHERE DATE(date) = DATE '2022-11-30'
) AS opt_out
FROM `students` s
WHERE bus LIKE 'Bus%' AND active = 'Yes'
ORDER BY sid;
Demo: https://dbfiddle.uk/TxyzF564