Sum of a joined table - mysql

Question

It is possible that this has been answered somewhere already but I couldn't find it.
So would appreciate if someone could help me with this sql statement again.
This is the sql statement which I have so far:
SELECT * , Round( (Rate * TIME_TO_SEC( Total ) /3600 ) , 2) AS revenue
FROM (SELECT event.eventID, event.staffID, event.role, TIMEDIFF( Time, Pause )
AS Total,
CASE WHEN Position = 'Teamleader'
THEN (Teamleader)
WHEN Position = 'Waiter'
THEN (Waiter)
ELSE '0'
END AS Rate
FROM event, rates, eventoverview
WHERE Storno =0
AND event.eventID= eventoverview.eventID
AND event.clientid = rates.clientid
GROUP BY event.eventID, event.clientID)q1
GROUP BY q1.staffID
The table I am getting is now giving me a total rate per staff and event.
But what I would like to achieve is a sum of those rates per staff.
So basically a sum of the revenue.
Hope someone can help me. Thanks in advance

Answer 1

You can enclose your query in a subquery and do that in the outer query like this:
SELECT *,
SUM(revenue)
FROM
(
SELECT * ,
Round( (Rate * TIME_TO_SEC( Total ) /3600 ) , 2) AS revenue
FROM
(
SELECT
event.eventID,
event.staffID,
event.role,
TIMEDIFF( Time, Pause ) AS Total,
CASE WHEN Position = 'Teamleader' THEN (Teamleader)
WHEN Position = 'Waiter' THEN (Waiter)
ELSE '0'
END AS Rate
FROM event
INNER JOIN rates ON event.clientid = rates.clientid
INNER JOIN eventoverview ON event.eventID = eventoverview.eventID
WHERE Storno =0
GROUP BY event.eventID, event.clientID
)q1
GROUP BY q1.staffID
) AS t
GROUP BY staffID;
Note that: You might get inconsistent data, due to the use of SELECT * with GROUP BY staffID only, the columns that are not in the GROUP BY clause need to be enclosed with an aggregate function otherwise mysql will get an arbitrary value for it. This is not recommended and it it is not the standard way to do so.