SQL Query that calculates time - sql

Question

Given these tables :
Item
-----
Id
Description
Status
CreatedBy
ItemLog
--------
Id
ItemId
NewStatus
TimeStamp
ChangedBy
Where Itemlog.ItemId = Item.Id, and Status = { "Created", "Pended", "Cancelled", "Completed" }...
How would you write a SQL query to generate the following results :
Item Description ChangeDate NewStatus ChangedBy
1 Test1 2012-01-01 Created User1
1 Test1 2012-01-02 Pended User2
1 Test1 2012-01-03 Completed User2
2 Test2 2012-01-01 Created User2
2 Test2 2012-01-02 Pended User3
2 Test2 2012-01-09 Cancelled User1
3 Test3 2012-01-01 Created User1
3 Test3 2012-01-02 Pended User1
Item CurrentUser CurrentStatus CreatedOn TotalTime TimePended CompletedDate CancelledDate
Test1 User2 Completed 2012-01-01 3 days 1 day 2012-01-03 (null)
Test2 User1 Completed 2012-01-01 9 days 7 days (null) 2012-01-09
Test3 User1 Pended 2012-01-01 35 days 34 days (null) (null)
Which I want to display as a master-detail report in my application.
The first resultset is a simple query with a couple of joins (I haven't included the UserId-UserName tables etc.)
The hard part is the calculation of the total times...
TimeToComplete is the TimeStamp of the last ItemLog minus the TimeStamp of the first ItemLog (where the ItemLog is ordered by date).
TimePended is the sum of the difference in TimeStamps between each change of the status from pended -> something.

Answer 1

Shazam!
create table Item(ID int, Description varchar(200),createdby varchar(20))
create table ItemLog(ID int, ItemID int, NewStatus varchar(200), [TimeStamp] datetime, ChangedBy varchar(20))
insert into Item(ID,Description,CreatedBy) values(1, 'Test 1', 'User1')
insert into Item(ID,Description,CreatedBy) values(2, 'Test 2', 'User1')
insert into Item(ID,Description,CreatedBy) values(3, 'Test 3', 'User1')
insert into ItemLog(ID, ItemID, NewStatus, TimeStamp, ChangedBy)
values(1,1,'Created','1/1/2012','User1')
insert into ItemLog(ID, ItemID, NewStatus, TimeStamp, ChangedBy)
values(2,1,'Pended','1/2/2012','User2')
insert into ItemLog(ID, ItemID, NewStatus, TimeStamp, ChangedBy)
values(3,1,'Completed','1/3/2012','User2')
insert into ItemLog(ID, ItemID, NewStatus, TimeStamp, ChangedBy)
values(4,2,'Created','1/1/2012','User2')
insert into ItemLog(ID, ItemID, NewStatus, TimeStamp, ChangedBy)
values(5,2,'Pended','1/2/2012','User3')
insert into ItemLog(ID, ItemID, NewStatus, TimeStamp, ChangedBy)
values(6,3,'Cancelled','1/9/2012','User1')
insert into ItemLog(ID, ItemID, NewStatus, TimeStamp, ChangedBy)
values(7,3,'Created','1/2/2012','User1')
insert into ItemLog(ID, ItemID, NewStatus, TimeStamp, ChangedBy)
values(8,3,'Pended','1/2/2012','User1')
select * from item i left outer join itemlog il on il.ItemID = i.ID
select
i.Description,
FirstStatusDate=minIL.TimeStamp,
CurrentStatus=maxIL.NewStatus,
CurrentStatusDate=maxIL.TimeStamp,
CurrentUser=maxIL.ChangedBy,
CompletedDate=(select max(TimeStamp) from ItemLog where ItemID=i.ID and NewStatus='Completed'),
[TotalTime (in days)]=case
when
minIL.TimeStamp is not null and maxIL.TimeStamp is not null
then datediff(day,minIL.TimeStamp,maxIL.TimeStamp)
else
convert(int,null)
end,
TimePending=sum(c.Days)
from
Item i
left outer join
(
select
y.ItemID,
y.MinDate,MinItemLogID=min(mn.id),
y.MaxDate,MaxItemLogID=max(mx.id)
from
(
select
ItemID,MinDate=min(timestamp), MaxDate=max(timestamp)
from
ItemLog il group by ItemID
) as y
left outer join ItemLog mn on mn.ItemID=y.ItemID and mn.TimeStamp=y.MinDate
left outer join ItemLog mx on mx.ItemID=y.ItemID and mx.TimeStamp=y.MaxDate
group by
y.ItemID, y.MinDate, y.MaxDate
)
z on z.ItemID = i.ID
left outer join ItemLog minIL on minIL.ID = z.MinItemLogID
left outer join ItemLog maxIL on maxIL.ID = z.MaxItemLogID
left outer join
(
select
p.ItemId,
PendTime=p.TimeStamp,
PendID=p.ID,
Days=datediff(day,p.TimeStamp,
coalesce(
(select min(TimeStamp)
from
ItemLog b
where
b.ItemID = P.ItemID and TimeStamp > p.TimeStamp )
,
getdate()
)
)
from
ItemLog p
where
p.NewStatus='Pended'
) c on c.ItemID = i.ID
group by
i.ID,
i.Description,
minIL.TimeStamp,
maxIL.NewStatus,
maxIL.TimeStamp,
maxIL.ChangedBy

Answer 2

Geez... Does that provide a big performance benefit over something like the following?
ALTER FUNCTION [dbo].[GetItemPendedTime]
(
-- Add the parameters for the function here
#ItemId uniqueidentifier
)
RETURNS INT
AS
BEGIN
-- Declare the return variable here
DECLARE #status INT
DECLARE #timespan datetime
DECLARE #pendTimeMinutes INT = 0
DECLARE #ispend bit = 0
DECLARE #lastTimespan datetime
DECLARE itemlog_queue CURSOR FOR
SELECT Status, Timestamp FROM ItemLog WHERE ItemId = #ItemId
OPEN itemlog_queue;
FETCH NEXT FROM itemlog_queue INTO #status, #timespan
WHILE ##FETCH_STATUS = 0
BEGIN
IF #ispend = 1
BEGIN
SET #pendTimeMinutes += DATEDIFF(minute, #lastTimespan, #timespan)
END
IF #status = 13
BEGIN
SET #ispend = 1
END
ELSE
BEGIN
SET #ispend = 0
END
SET #lastTimespan = #timespan
FETCH NEXT FROM itemlog_queue INTO #status, #timespan
END
CLOSE itemlog_queue
DEALLOCATE itemlog_queue
IF #ispend = 1
BEGIN
SET #pendTimeMinutes = #pendTimeMinutes + DATEDIFF(minute, #lastTimespan, GETDATE())
END
-- Return the result of the function
RETURN #pendTimeMinutes
END
And then call it like
SELECT Description, Status as CurrentStatus, dbo.GetItemPendedTime(ItemId) FROM Items