SQL - How to combine rows - sql-server

Question

I have the following table which looks at calls and attendances. I got this by using union all on a 'calls' and 'attendances' tables and then used row number on the ID and ordered by dates.
Table1:
Type | ID | Call/AttendanceDate | RowNum
------------|----|---------------------|--------
Attendance | 12 | 2018-09-16 10:11:00 | 82
Call | 12 | 2018-09-18 14:11:47 | 83
Call | 12 | 2018-10-02 17:26:13 | 84
Call | 12 | 2018-10-05 14:58:31 | 85
Attendance | 12 | 2018-10-13 01:41:00 | 86
Call | 12 | 2018-10-13 02:39:12 | 87
Call | 12 | 2018-10-13 04:31:22 | 88
Attendance | 12 | 2018-10-13 14:29:00 | 89
Call | 12 | 2018-10-13 14:59:19 | 90
Attendance | 12 | 2018-10-15 15:50:00 | 91
The code I used for this is:
WITH CTE1 AS
(
SELECT 'Call' as [Type], ID, CallDate AS Date1
FROM CallsTable
UNION ALL
SELECT 'Attendance' as [Type], ID, AttendanceDate AS Date2
FROM AttendanceTable]
)
,CTE2 AS
(
SELECT [Type], Date1, ID, ROW_NUMBER() OVER (PARTITION BY ID ORDER BY Date1 ASC) AS RowNum
FROM CTE1
)
--------------------------------OUTPUT--------------------------------
SELECT a.[Type], a.ID, a.Date1, a.RowNum
FROM CTE2 a
JOIN CTE2 b
ON a.ID= b.ID
AND a.RowNum = b.RowNum + 1
WHERE a.ID = '12'
ORDER BY ID, RowNum
I want to modify this to look like the below output, so that whenever an attendance follows a call, it should be in the same row.
Table2:
Type | ID | CallDate | RowNum | Type | AttendanceDate | RowNum
------|----|------------------|--------|------------|------------------|--------
NULL | 12 | NULL | NULL | Attendance | 16/09/2018 10:11 | 82
Call | 12 | 18/09/2018 14:11 | 83 | NULL | NULL | NULL
Call | 12 | 02/10/2018 17:26 | 84 | NULL | NULL | NULL
Call | 12 | 05/10/2018 14:58 | 85 | Attendance | 13/10/2018 01:41 | 86
Call | 12 | 13/10/2018 02:39 | 87 | NULL | NULL | NULL
Call | 12 | 13/10/2018 04:31 | 88 | Attendance | 13/10/2018 14:29 | 89
Call | 12 | 13/10/2018 14:59 | 90 | Attendance | 15/10/2018 15:50 | 91
Is this possible? What code could I use?

Answer 1

Use FULL JOIN
SELECT
*
FROM
(SELECT * FROM CTE2 WHERE Type = 'CALL') A
FULL JOIN
(SELECT * FROM CTE2 WHERE Type = 'ATTENDANCE') B
ON A.ID = B.ID AND A.RowNum = B.RowNum - 1

Answer 2

You can use APPLY :
SELECT C.[Type], C.ID, C.CallDate, C.RowNum,
(CASE WHEN C2.RowNum - C.RowNum = 1 THEN C2.[TYPE] end) [TYPE],
(CASE WHEN C2.RowNum - C.RowNum = 1 THEN C2.CallDate end) AttendanceDate,
(CASE WHEN C2.RowNum - C.RowNum = 1 THEN C2.RowNum end) RowNum
FROM CTE2 C OUTER APPLY
(SELECT TOP (1) C2.*
FROM CTE2 C2
WHERE C2.ID = C.ID AND C2.[Type] = 'Attendance' AND C2.RowNum > C.RowNum
ORDER BY C2.RowNum
) C2
WHERE C.ID = 12 AND C.[Type] = 'Call';

Answer 3

Not as elegant, but works for me, a table valued function
alter FUNCTION GetCallActivity()
RETURNS #activityTable TABLE
(
call_type varchar(16),
call_id int,
call_date datetime,
call_rownum int,
atnd_type varchar(16),
atnd_id int,
atnd_date datetime,
atnd_rownum int
)
AS
BEGIN
-- initialize the return table
insert into #activityTable
(call_type, call_id, call_date, call_rownum )
select a.type, a.id, a.activity_date, a.rownum
from stack_calls a
where a.type = 'Call'
order by a.activity_date;
-- match to the attendence recs to the call recs
update #activityTable
set atnd_type = b.type,
atnd_id = b.id,
atnd_date = b.activity_date,
atnd_rownum = b.rownum
from stack_calls b
join #activityTable a
on b.rownum = a.call_rownum + 1
where b.type = 'Attendance';
-- deal with the edge cases
insert into #activityTable
( atnd_type, atnd_id, atnd_date, atnd_rownum )
select x.type,
x.id,
x.activity_date,
x.rownum
from
(
select a.type,
a.id,
a.activity_date,
a.rownum,
lag(a.type, 1) over (order by a.activity_date) as prev_type
from stack_calls a
where a.type = 'Attendance'
) x
where x.prev_type is null
RETURN
END
GO