MySQL 8.0

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CREATE TABLE tt
(
  mycall varchar(30),
  tid datetime,
  mm varchar(30),
  conf int
);

INSERT INTO tt(mycall ,tid, mm, conf)
VALUES('SM6ABC', '2022-04-01 09:00:00', 'AAAA', 1),
('SM6ABC', '2022-04-01 09:01:00', 'AAAB', 1),
('SM6ABC', '2022-04-01 09:12:00', 'AAAA', 1),
('SM6CBA', '2022-04-01 09:10:00', 'BBBB', 1),
('SM6CBA', '2022-04-01 09:11:00', 'AAAA', 1),
('SM6AAA', '2022-04-01 09:12:00', 'AAAA', 1);
SELECT *
FROM tt;


mycall
tid
mm
conf


SM6ABC
2022-04-01 09:00:00
AAAA
1

SM6ABC
2022-04-01 09:01:00
AAAB
1

SM6ABC
2022-04-01 09:12:00
AAAA
1

SM6CBA
2022-04-01 09:10:00
BBBB
1

SM6CBA
2022-04-01 09:11:00
AAAA
1

SM6AAA
2022-04-01 09:12:00
AAAA
1


SELECT mycall, MAX(tid) AS 'tid', COUNT(DISTINCT mm) AS 'total'
FROM tt
WHERE mm !='' AND conf = '1'
GROUP BY mycall
ORDER BY total DESC


mycall
tid
total


SM6ABC
2022-04-01 09:12:00
2

SM6CBA
2022-04-01 09:11:00
2

SM6AAA
2022-04-01 09:12:00
1

mycall	tid	mm	conf
SM6ABC	2022-04-01 09:00:00	AAAA	1
SM6ABC	2022-04-01 09:01:00	AAAB	1
SM6ABC	2022-04-01 09:12:00	AAAA	1
SM6CBA	2022-04-01 09:10:00	BBBB	1
SM6CBA	2022-04-01 09:11:00	AAAA	1
SM6AAA	2022-04-01 09:12:00	AAAA	1