找出2人之间发生的通话总时长

Question

I want to find out the call duration between 2 persons through SQL. Say "Joe" calling "Mak" and spoke 5 minutes and "Mak" calling "Joe" for 15 minutes then total duration must be 20 minutes.

I tried something with self join but getting duplicates for such calls.

SELECT t1.cal1, t2.cal2,sum(t1.dur) as Total 
from tele t1
INNER JOIN   tele t2
ON (t1.cal1 = t2.cal1 AND t1.cal2 = t2.cal2)
GROUP BY T1.CAL1, T2.CAL2;

cal1       cal2    duration (in Mins)
A           B        5
A           B       10
B           A       10
B           A       25
A           D        1
D           C        2
B           C        4
C           B        9
C           B        7
C           A        2
D           C        5
D           B       10

Answer 1

The simpler way is to use CASE so you get the unique combinations of col1 and col2 and then group by each combination:

SELECT 
  case when cal1 < cal2 then cal1 else cal2 end col1, 
  case when cal1 < cal2 then cal2 else cal1 end col2, 
  SUM(duration) duration
FROM tele 
GROUP BY col1, col2

See the demo .
Results:

> col1 | col2 | duration
> :--- | :--- | -------:
> A    | B    |       50
> A    | C    |        2
> A    | D    |        1
> B    | C    |       20
> B    | D    |       10
> C    | D    |        7

In case you use SQLServer, you need this:

SELECT 
  case when cal1 < cal2 then cal1 else cal2 end col1, 
  case when cal1 < cal2 then cal2 else cal1 end col2, 
  SUM(duration) duration
FROM tele 
GROUP BY 
  case when cal1 < cal2 then cal1 else cal2 end, 
  case when cal1 < cal2 then cal2 else cal1 end

or replace the CASE statements with

Answer 2

You will have to dynamically set your columns in a subquery and group the results of it again to achieve your desired outcome:

SELECT 
  col1, col2, SUM(duration) 
FROM 
  (
    SELECT 
      IF(cal1 < cal2, cal1, cal2) AS col1, 
      IF(cal1 < cal2, cal2, cal1) AS col2, 
      SUM(duration) AS duration
    FROM 
      tel 
    GROUP BY 
      cal1, 
      cal2
  ) AS m 
GROUP BY 
  col1, 
  col2

Answer 3

If a call A to B is equivalent to B to A, then it would probably help if you create a combined column consisting of both parties names - eg AB - with the order of the names in the combination determined by the sort order of the strings.

So for example, CASE WHEN A < B THEN A + B ELSE B + A END AS party_names .

This will ensure both calls from A to B, and calls from B to A, result in a party_names of AB.

You can then GROUP BY and SELECT that column, and SUM(duration).

Answer 4

Most databases support least() and greatest() :

select least(t.cal1, t2.cal2), greatest(t.cal1, t2.cal2),
       sum(t1.dur) as Total 
from tele t1 
group by least(t.cal1, t2.cal2), greatest(t.cal1, t2.cal2);

For databases that do not, you can use a case expression instead.