MYSQL GROUP BY multiple derived tables? - mysql

Question

I have this query which does some calculations based on some derived tables that are linked with an INNER JOIN.
At the moment I have a WHERE clause which pulls out one id at a time. But how can I make it list all the ids?
I have tried GROUP BY in various places but can't figure it out.
My query so far is as follows:
SELECT
equipment_id,
service_duration,
available_duration,
(available_duration / service_duration)*100 AS availability
FROM (
SELECT
SUM(service_end_time - service_start_time) AS service_duration
FROM(
SELECT equipment_id,
(CASE
END) AS service_start_time,
(CASE
END) AS service_end_time
FROM t1
WHERE equipment_id = 'EX123'
)AS A
) AS B
JOIN(
SELECT equipment_id,
SUM(available_end_time - available_start_time) AS available_duration
FROM (
SELECT equipment_id,
(CASE
END) AS available_start_time,
(CASE
END) AS available_end_time
FROM t2
WHERE equipment_id = 'EX123'
) AS C
) AS D
ON equipment_id=D.equipment_id
What I want to do is replace the WHERE clause with a GROUP BY to list all the ids, or similar, but getting that to work is beyond my skill level... Any help greatly appreciated :)

Answer 1

Try below:
SELECT
equipment_id, service_duration, available_duration,
(available_duration / service_duration)*100 AS availability
FROM
(
SELECT equipment_id,
SUM(service_end_time - service_start_time) AS service_duration
FROM
(
SELECT equipment_id,
(CASE ... END) AS service_start_time,
(CASE ... END) AS service_end_time
FROM t1
) AS A
GROUP BY equipment_id
) AS B
JOIN
(
SELECT equipment_id,
SUM(available_end_time - available_start_time) AS available_duration
FROM
(
SELECT equipment_id,
(CASE ... END) AS available_start_time,
(CASE ... END) AS available_end_time
FROM t2
) AS C
GROUP BY equipment_id
) AS D
ON equipment_id=D.equipment_id

Answer 2

Try this (replace my field names with your field names):
SELECT
a.emp_id,
service_duration,
available_duration
FROM
(
SELECT
emp_id,
SUM(service_end_time - service_start_time) AS service_duration
FROM
data
GROUP BY
emp_id
) a
JOIN
(
SELECT
emp_id,
SUM(available_end_time - available_start_time) AS available_duration
FROM
data
GROUP BY
emp_id
) b
ON a.emp_id = b.emp_id
GROUP BY
a.emp_id