Tsrange - Calculating the difference between two ranges

问题

I have two tables free_time and appointment. Both contain tsranges.

How do I write a query (or function) that determines the actual free time after "subtracting" the difference the appointment from the freetime?

INSERT INTO free_time(freetime)
VALUES('[2017-04-19 09:00, 2017-04-19 12:30)');

INSERT INTO appointment(appointment)
VALUES('[2017-04-19 10:30, 2017-04-19 11:30)');

I want the result to be something like:

["2017-04-19 9:00","2017-04-19 10:30:00"), 
["2017-04-19 11:30:00","2017-04-19 12:30:00")

回答1:

You'll have to break apart the range, from the docs

The union and difference operators will fail if the resulting range would need to contain two disjoint sub-ranges, as such a range cannot be represented.

In order to do this you can use lower, and upper

SELECT tsrange(  lower(freetime), lower(appointment)  )  AS before_appointment,
       tsrange(  upper(appointment), upper(freetime)  )  AS after_appointment
FROM ( VALUES
  (
    '[2017-04-19 09:00, 2017-04-19 12:30)'::tsrange,
    '[2017-04-19 10:30, 2017-04-19 11:30)'::tsrange
  )
) AS t(freetime,appointment)
WHERE freetime @> appointment;

              before_appointment               |               after_appointment               
-----------------------------------------------+-----------------------------------------------
 ["2017-04-19 09:00:00","2017-04-19 10:30:00") | ["2017-04-19 11:30:00","2017-04-19 12:30:00")
(1 row)

来源：https://stackoverflow.com/questions/43502687/tsrange-calculating-the-difference-between-two-ranges