MySQL 8.0

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CREATE TABLE `contract` (
`id` int(11) NOT NULL AUTO_INCREMENT,
`emp_id` int(11) DEFAULT NULL ,
`sign_time` datetime DEFAULT NULL ,
`end_time` datetime DEFAULT NULL ,
PRIMARY KEY (`id`)
) ENGINE=InnoDB DEFAULT CHARSET=utf8 ;
INSERT INTO `contract` (`id`, `emp_id`,`sign_time`, `end_time`) 
VALUES 
   ('25', '83', '2018-11-21 00:00:00', '2018-12-01 15:27:00')
,  ('26', '94', '2018-11-21 00:00:00', '2018-12-01 15:23:00');

Records: 2  Duplicates: 0  Warnings: 0


CREATE TABLE `employee_detail` (
`id` int(11) NOT NULL AUTO_INCREMENT,
`name` varchar(100) DEFAULT NULL ,
 `stage` varchar(100) DEFAULT NULL ,
 PRIMARY KEY (`id`)
 ) ENGINE=InnoDB DEFAULT CHARSET=utf8 ;
INSERT INTO `employee_detail` (`id`, `name`, `stage`)
VALUES
  ('83', 'Michael', '1')
, ('94', 'John', '1');

Records: 2  Duplicates: 0  Warnings: 0


SELECT
    c.*
    , TIMESTAMPDIFF(MONTH,'2018-11-30 09:18:23',c.end_time)  diff_month1
    , case when TIMESTAMPDIFF(MONTH,'2018-11-30 09:18:23',c.end_time) = 0 then 'equal'
           when TIMESTAMPDIFF(MONTH,'2018-11-30 09:18:23',c.end_time) > 0 then 'greater'
      end diff_month
    , TIMESTAMPDIFF(MINUTE,'2018-11-30 09:18:23',c.end_time) diff_minute1
    , case when TIMESTAMPDIFF(MINUTE,'2018-11-30 09:18:23',c.end_time) = 0 then 'equal'
           when TIMESTAMPDIFF(MINUTE,'2018-11-30 09:18:23',c.end_time) > 0 then 'greater'
      end diff_minute
FROM contract c
JOIN employee_detail e ON c.emp_id = e.id
where TIMESTAMPDIFF(MONTH ,'2018-11-30 09:18:23',c.end_time) = 0
  and TIMESTAMPDIFF(MINUTE,'2018-11-30 09:18:23',c.end_time) = 0


id
emp_id
sign_time
end_time
diff_month1
diff_month
diff_minute1
diff_minute


25
83
2018-11-21 00:00:00
2018-12-01 15:27:00
0
equal
1808
greater

26
94
2018-11-21 00:00:00
2018-12-01 15:23:00
0
equal
1804
greater


SELECT
    c.*
    , TIMESTAMPDIFF(MONTH,'2018-11-30 09:18:23',c.end_time)  diff_month1
    , case when TIMESTAMPDIFF(MONTH,'2018-11-30 09:18:23',c.end_time) = 0 then 'equal'
           when TIMESTAMPDIFF(MONTH,'2018-11-30 09:18:23',c.end_time) > 0 then 'greater'
      end diff_month
    , TIMESTAMPDIFF(MINUTE,'2018-11-30 09:18:23',c.end_time) diff_minute1
    , case when TIMESTAMPDIFF(MINUTE,'2018-11-30 09:18:23',c.end_time) = 0 then 'equal'
           when TIMESTAMPDIFF(MINUTE,'2018-11-30 09:18:23',c.end_time) > 0 then 'greater'
      end diff_minute
FROM contract c
JOIN employee_detail e ON c.emp_id = e.id
where TIMESTAMPDIFF(MINUTE,'2018-11-30 09:18:23',c.end_time) = 0
  and TIMESTAMPDIFF(MONTH ,'2018-11-30 09:18:23',c.end_time) = 0


id
emp_id
sign_time
end_time
diff_month1
diff_month
diff_minute1
diff_minute
id	emp_id	sign_time	end_time	diff_month1	diff_month	diff_minute1	diff_minute
25	83	2018-11-21 00:00:00	2018-12-01 15:27:00	0	equal	1808	greater
26	94	2018-11-21 00:00:00	2018-12-01 15:23:00	0	equal	1804	greater