TIMESTAMPDIFF Sum Case error - mysql

Question

+-----------+-----------+--------+
| punchtime | punchdate | emp_id |
+-----------+-----------+--------+
| 9:51:00 | 4/1/2016 | 2 |
| 12:59:00 | 4/1/2016 | 2 |
| 10:28:00 | 4/1/2016 | 5 |
| 14:13:00 | 4/1/2016 | 5 |
| 9:56:00 | 4/1/2016 | 10 |
| 15:31:00 | 4/1/2016 | 10 |
| 10:08:00 | 5/1/2016 | 2 |
| 18:09:00 | 5/1/2016 | 2 |
| 10:15:00 | 5/1/2016 | 5 |
| 18:32:00 | 5/1/2016 | 5 |
| 10:11:00 | 6/1/2016 | 2 |
| 18:11:00 | 6/1/2016 | 2 |
| 10:25:00 | 6/1/2016 | 5 |
| 18:28:00 | 6/1/2016 | 5 |
| 10:19:00 | 6/1/2016 | 10 |
| 18:26:00 | 6/1/2016 | 10 |
+-----------+-----------+--------+
I need to count where emp_id punchtime is less then that 4 hours and count ir for the whole. i am trying the below code but its not working.
SELECT
a.emp_id,
sum( case when TIMESTAMPDIFF(hour, min(a.punchtime),
max(a.punchtime))< 4 then 1 else 0 end ) as 'Half Day'
FROM machinedata a
GROUP BY
a.emp_id
I am getting a error #1111 - Invalid use of group function
Desired output -
+-----------+-----------+
| emp_id | Half Day |
+-----------+-----------+
|2 | 1 |
|8 | 0 |
|10 |0 |
+-----------+-----------+

Answer 1

Your data set and desired result do not accord, so I'm going to ignore it...
Instead consider the following...
Note both the way in which I have presented the problem, and the construction of the solution.
DROP TABLE IF EXISTS my_table;
CREATE TABLE my_table
(employee_id INT NOT NULL
,punchtime DATETIME NOT NULL
,PRIMARY KEY(employee_id,punchtime)
);
INSERT INTO my_table VALUES
( 2,'2016/01/04 09:51:00'),
( 2,'2016/01/04 12:59:00'),
( 5,'2016/01/04 10:28:00'),
( 5,'2016/01/04 14:13:00'),
(10,'2016/01/04 09:56:00'),
(10,'2016/01/04 15:31:00'),
( 2,'2016/01/05 10:08:00'),
( 2,'2016/01/05 18:09:00'),
( 5,'2016/01/05 10:15:00'),
( 5,'2016/01/05 18:32:00'),
( 2,'2016/01/06 10:11:00'),
( 2,'2016/01/06 18:11:00'),
( 5,'2016/01/06 10:25:00'),
( 5,'2016/01/06 18:28:00'),
(10,'2016/01/06 10:19:00'),
(10,'2016/01/06 18:26:00');
SELECT employee_id
, SUM(diff < 14400 ) half
FROM
( SELECT x.*
, DATE(x.punchtime) dt
, TIME_TO_SEC(MAX(y.punchtime)) - TIME_TO_SEC(MIN(x.punchtime)) diff
FROM my_table x
JOIN my_table y
ON y.employee_id = x.employee_id
AND DATE(y.punchtime) = DATE(x.punchtime)
GROUP
BY x.employee_id
, dt
) n
GROUP
BY employee_id;
+-------------+------+
| employee_id | half |
+-------------+------+
| 2 | 1 |
| 5 | 1 |
| 10 | 0 |
+-------------+------+