Extending a Pivot - sql-server

Question

I have a Documents table and an Events table.
Documents table has ID and a bunch of other fields not relevant to
this question.
Events table has DocID, EventType, EventDate, and UserID.
A document may have zero or more Events of any of these EventTypes:
0 = Created
1 = Modified
2 = Submitted
3 = Approved
DocID | EventType | EventDate | UserID
-----------------------------------------------
1 | 0 | 1-2-2017 | 123
1 | 1 | 1-3-2017 | 456
1 | 1 | 1-4-2017 | 489
1 | 2 | 1-5-2017 | 357
2 | 0 | 1-6-2017 | 951
2 | 1 | 1-7-2017 | 654
2 | 2 | 1-8-2017 | 654
2 | 3 | 1-9-2017 | 357
Pivoting the Events table is easy enough:
SELECT DocID, [0] AS CreatedDate, [1] AS ModifiedDate,
[2] AS SubmittedDate, [3] AS ApprovedDate
FROM (SELECT DocID, EventType, EventDate FROM Events
WHERE DocID IS NOT NULL AND EventDate IS NOT NULL) AS DocEvents
PIVOT (MAX(EventDate) FOR EventType IN ([0], [1], [2], [3]))
AS DocEventsPivot
For my purposes, the most recent event of a given type is wanted, thus the MAX aggregate:
DocID | CreatedDate | ModifiedDate | SubmittedDate | ApprovedDate
-----------------------------------------------------------------
1 | 1-2-2017 | 1-4-2017 | 1-5-2017 | NULL
2 | 1-6-2017 | 1-7-2017 | 1-8-2017 | 1-9-2017
How can I get the UserID translated to CreatedBy, ModifiedBy, SubmittedBy, and ApprovedBy to correspond to the dates of the appropriate EventType?
I will not know the possible values of UserID in advance.
Desired Output:
DocID | CreatedDate | ModifiedDate | SubmittedDate | ApprovedDate | CreatedBy | ModifiedBy | SubmittedBy | ApprovedBy
---------------------------------------------------------------------------------------------------------------------
1 | 1-2-2017 | 1-4-2017 | 1-5-2017 | NULL | 123 | 489 | 357 | NULL
2 | 1-6-2017 | 1-7-2017 | 1-8-2017 | 1-9-2017 | 951 | 654 | 654 | 657

Answer 1

Rather than using PIVOT another solution is using OUTER APPLY.
CREATE TABLE #Documents (ID int)
CREATE TABLE #Events (DocID int, EventType int, EventDate date, UserID int)
INSERT INTO #Documents VALUES
(1),
(2)
INSERT INTO #Events VALUES
(1, 0, '1-2-2017', 123),
(1, 1, '1-3-2017', 456),
(1, 1, '1-4-2017', 489),
(1, 2, '1-5-2017', 357),
(2, 0, '1-6-2017', 951),
(2, 1, '1-7-2017', 654),
(2, 2, '1-8-2017', 654),
(2, 3, '1-9-2017', 357)
SELECT
DOC.ID AS 'DocID',
CRT.EventDate AS 'CreatedDate',
MFY.EventDate AS 'ModifiedDate',
SUB.EventDate AS 'SubmittedDate',
APR.EventDate AS 'ApprovedDate',
CRT.UserID AS 'CreatedBy',
MFY.UserID AS 'ModifiedBy',
SUB.UserID AS 'SubmittedBy',
APR.UserID AS 'ApprovedBy'
FROM
#Documents AS DOC
OUTER APPLY (SELECT TOP 1 EventDate, UserID FROM #Events WHERE DocID = DOC.ID AND EventType = 0 ORDER BY EventDate DESC) AS CRT
OUTER APPLY (SELECT TOP 1 EventDate, UserID FROM #Events WHERE DocID = DOC.ID AND EventType = 1 ORDER BY EventDate DESC) AS MFY
OUTER APPLY (SELECT TOP 1 EventDate, UserID FROM #Events WHERE DocID = DOC.ID AND EventType = 2 ORDER BY EventDate DESC) AS SUB
OUTER APPLY (SELECT TOP 1 EventDate, UserID FROM #Events WHERE DocID = DOC.ID AND EventType = 3 ORDER BY EventDate DESC) AS APR
DROP TABLE #Documents
DROP TABLE #Events

Answer 2

Try the following
CREATE TABLE #Events (DocID int, EventType int, EventDate date, UserID int)
INSERT INTO #Events VALUES
(1, 0, '1-2-2017', 123),
(1, 1, '1-3-2017', 456),
(1, 1, '1-4-2017', 489),
(1, 2, '1-5-2017', 357),
(1, 2, '1-4-2017', 666),
(2, 0, '1-6-2017', 951),
(2, 1, '1-7-2017', 654),
(2, 2, '1-8-2017', 654),
(2, 3, '1-9-2017', 357)
SELECT
DocID,
MAX(CASE WHEN EventType=0 THEN EventDate END) [CreatedDate],
MAX(CASE WHEN EventType=1 THEN EventDate END) [ModifiedDate],
MAX(CASE WHEN EventType=2 THEN EventDate END) [SubmittedDate],
MAX(CASE WHEN EventType=3 THEN EventDate END) [ApprovedDate],
MAX(CASE WHEN EventType=0 THEN LastUserID END) [CreatedBy],
MAX(CASE WHEN EventType=1 THEN LastUserID END) [ModifiedBy],
MAX(CASE WHEN EventType=2 THEN LastUserID END) [SubmittedBy],
MAX(CASE WHEN EventType=3 THEN LastUserID END) [ApprovedBy]
FROM
(
SELECT
DocID,
EventDate,
EventType,
LAST_VALUE(UserID)OVER(
PARTITION BY DocID,EventType
ORDER BY EventDate
ROWS BETWEEN UNBOUNDED PRECEDING AND UNBOUNDED FOLLOWING
) LastUserID
FROM #Events
) q
GROUP BY DocID
DROP TABLE #Events
Or you can use IFF instead CASE. I prefer use CASE because it isn't block ELSE
SELECT
DocID,
MAX(IIF(EventType=0,EventDate,NULL)) [CreatedDate],
MAX(IIF(EventType=1,EventDate,NULL)) [ModifiedDate],
MAX(IIF(EventType=2,EventDate,NULL)) [SubmittedDate],
MAX(IIF(EventType=3,EventDate,NULL)) [ApprovedDate],
MAX(IIF(EventType=0,LastUserID,NULL)) [CreatedBy],
MAX(IIF(EventType=1,LastUserID,NULL)) [ModifiedBy],
MAX(IIF(EventType=2,LastUserID,NULL)) [SubmittedBy],
MAX(IIF(EventType=3,LastUserID,NULL)) [ApprovedBy]
FROM
(
SELECT
DocID,
EventDate,
EventType,
LAST_VALUE(UserID)OVER(
PARTITION BY DocID,EventType
ORDER BY EventDate
ROWS BETWEEN UNBOUNDED PRECEDING AND UNBOUNDED FOLLOWING
) LastUserID
FROM #Events
) q
GROUP BY DocID