Mysql 计算 Sum(if()) 中的不同 ID

Question

I have following tables.

Case

ID	Name
1	Anton
2	Elfriede
3	Osram

Appointments

ID	Duration	Case
1	70	1
2	70	2

Fastdocu with out appointment

ID	Duration	Case
1	15	2
2	15	2
3	50	3
3	8	3

I need sum up all duration and all appointments and the cases that are not in Appointments.

The result should be

Duration 88
Appointments 3
Cases 1

Following Statement I have written

Select sum(duration), count(DISTINCT ID), SUM(IF(`Case` NOT IN (1,2),1,0)) From Fastdocu

Suddenly the result is

Duration 88
Appointments 3
Cases 2

I must sum only distinct ids at the cases count. But the distinct seems to be forbidden in the if. How can I count the cases right?

Answer 1

Use COUNT() with a CASE expression instead of SUM() :

SELECT SUM(duration) total_duration, 
       COUNT(DISTINCT ID) distinct_ids, 
       COUNT(DISTINCT CASE WHEN `Case` NOT IN (1,2) THEN `Case` END) cases_not_in_Appointments 
FROM Fastdocu

Since COUNT() does not have an ELSE branch it will not count Case s that do not satisfy the condition Case NOT IN (1,2) because in this case the result of the CASE expression will be NULL .

If you want to count the distinct id s and not the distinct Case s change to:

COUNT(DISTINCT CASE WHEN `Case` NOT IN (1,2) THEN ID END) 

See the demo .
Results:

total_duration	distinct_ids	cases_not_in_Appointments
88	3	1