Extract values with stored procedure in SQL Server [closed] - sql

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I need your help to create a view in SQL Server (v12.0.6024.0). One of my customer has a table in which some time slot are saved in this format:
ID
ID_EVENT
Time Slot
1000
24
08:30:00.0000
1000
24
09:00:00.0000
1000
24
09:30:00.0000
Every time slot lasts 30 minutes, the example above means that event with ID 24 (saved in another table) lasted form 8:30 to 10:00 (3rd slot started at 9:30, lasted 30 minutes so it finished at 10:00). The problem is that in some cases the time values are not consecutive and there may be a pause in the middle, so I would have something like this:
ID
ID_EVENT
Time Slot
1000
24
08:30:00.0000
1000
24
09:00:00.0000
1000
24
09:30:00.0000
1000
24
11:30:00.0000
1000
24
12:00:00.0000
1000
24
12:30:00.0000
In this case event with ID 24 lasted from 8:30 to 10, stopped, then started again from 11:30 to 13:00. I have been asked to prepare a view for an external developer in which I have to report not only the time the event started (in my example, 8:30) and the time it stopped for good (in my example 13:00) but also the time the pause started (in my example 10:00) and the time the pause finished (in my example 11:30).
I have no problem with the first 2 values but I don't know how to extract the other two. I think we can consider a pause happening when 2 time slots are not consecutive, there cannot be more than periods for the same event. I suppose I need a procedure but find it difficult to write it; I need to have a view that says
ID
ID_EVENT
Time1
Time2
Time3
Time4
1000
24
08:30:00.0000
10:00:00.0000
11:30:00.0000
13:00:00.0000
Any help?

Answer 1

declare #t table(ID int, ID_EVENT int, TimeSlot time)
insert into #t
values
(1000, 24, '08:30:00.0000'),
(1000, 24, '09:00:00.0000'),
(1000, 24, '09:30:00.0000'),
--
(1000, 24, '11:30:00.0000'),
(1000, 24, '12:00:00.0000'),
(1000, 24, '12:30:00.0000'),
--
(1000, 24, '15:00:00.0000'),
(1000, 24, '15:30:00.0000'),
(1000, 24, '16:00:00.0000'),
--
(1000, 25, '15:30:00.0000'),
(1000, 25, '16:30:00.0000');
select Id, ID_EVENT,
min(TimeSlot) as StartTimeSlot,
dateadd(minute, 30, max(TimeSlot)) as EndTimeSlot
from
(
select *,
datediff(minute, '00:00:00', Timeslot)/30 - row_number() over(partition by Id, ID_EVENT order by TimeSlot) as grpid
from #t
) as t
group by Id, ID_EVENT, grpid;
--first two groups per event&id row
select Id, ID_EVENT,
--1
min(case when grpordinal = 1 then TimeSlot end) as StartSlot1,
dateadd(minute, 30, max(case when grpordinal = 1 then TimeSlot end)) as EndSlot1,
--2
min(case when grpordinal = 2 then TimeSlot end) as StartSlot2,
dateadd(minute, 30, max(case when grpordinal = 2 then TimeSlot end)) as EndSlot2
from
(
select Id, ID_EVENT, TimeSlot,
dense_rank() over(partition by Id, ID_EVENT order by grpid) as grpordinal
from
(
select *,
datediff(minute, '00:00:00', Timeslot)/30 - row_number() over(partition by Id, ID_EVENT order by TimeSlot) as grpid
from #t
) as t
) as src
--where grpordinal <= 2 --not really needed
group by Id, ID_EVENT;
--!!!!only when there are max two groups/periods
--if there could be more than 2 periods this will not work
select Id, ID_EVENT,
--1
min(case when grpid = 0 then TimeSlot end) as StartSlot1,
dateadd(minute, 30, max(case when grpid = 0 then TimeSlot end)) as EndSlot1,
--2
min(case when grpid <> 0 then TimeSlot end) as StartSlot2,
dateadd(minute, 30, max(case when grpid <> 0 then TimeSlot end)) as EndSlot2
from
(
select *,
/*
1
+ datediff(minute, '00:00:00', Timeslot)/30 - row_number() over(partition by Id, ID_EVENT order by TimeSlot)
- datediff(minute, '00:00:00', min(Timeslot) over(partition by Id, ID_EVENT)) /30
*/
1
+ datediff(minute, min(Timeslot) over(partition by Id, ID_EVENT), TimeSlot)/30
- row_number() over(partition by Id, ID_EVENT order by TimeSlot)
as grpid --1st groupid is always 0
from #t
) as t
group by Id, ID_EVENT;

Answer 2

This reads like a gaps-and-islands problem, where you want to identify and group together "adjacent" time slots.
I would suggest putting the ranges in rows rather than in column. For this, you can use window functions like that:
select id, id_event,
min(timeslot) as timeslot_start, max(timeslot) as timeslot_end
from (
select t.*,
row_number() over(partition by id, id_event order by timeslot) rn
from mytable t
) t
group by id, id_event, datediff(minute, - rn * 30, timeslot)
If want to see the first two ranges per event only - both on the same row in the resultset - then we can use conditional aggregation on top of that query:
select id, id_event,
max(case when rn = 1 then timeslot_start end) as timeslot_start_1,
max(case when rn = 1 then timeslot_end end) as timeslot_end_1,
max(case when rn = 2 then timeslot_start end) as timeslot_start_2,
max(case when rn = 2 then timeslot_end end) as timeslot_end_2
from (
select id, id_event,
min(timeslot) as timeslot_start, max(timeslot) as timeslot_end,
row_number() over(partition by id, id_event order by min(timeslot)) rn
from (
select t.*,
row_number() over(partition by id, id_event order by timeslot) rn
from mytable t
) t
group by id, id_event, datediff(minute, - rn * 30, timeslot)
) t
where rn <= 2
group by id, id_event