Table:
0
A
B
C
D
1
order id
customer id
order status code
order date
2
1
12
Completed
2/10/2018 15:44
3
2
4
New
1/31/2018 17:49
4
3
1
PartFilled
2/26/2018 12:39
5
4
4
Pending
3/7/2018 16:55
6
5
4
New
2/12/2018 19:34
7
6
11
PartFilled
3/6/2018 16:35
8
7
1
Cancelled
2/15/2018 2:25
9
8
13
Pending
3/5/2018 23:17
10
9
7
Pending
2/9/2018 11:16
11
10
11
Cancelled
3/22/2018 10:49
12
11
8
Cancelled
2/16/2018 19:42
13
12
4
New
2/2/2018 23:42
14
13
15
PartFilled
2/26/2018 5:34
15
14
6
Completed
3/18/2018 15:12
16
15
10
Pending
3/16/2018 22:42

Questions and formulas:
Question: List the order id, customer id in Cancelled status, ordered by their order dates.
Formula: SORT(LET(query1,FILTER(A1:D1,C1="cancelled"),UNIQUE(CHOOSECOLS(query1,1,2,4))), 3, 1)
Formula2: SORT(LET(query1,FILTER(A2:D16,C2:C16="cancelled"),UNIQUE(CHOOSECOLS(query1,1,2,4))), 3, 1)
Level: hard
Question: What are the order ids and customer ids that have been Cancelled, sorted by their order dates?
Formula: SORT(LET(query1,FILTER(A1:D1,C1="cancelled"),UNIQUE(CHOOSECOLS(query1,1,2,4))), 3, 1)
Formula2: SORT(LET(query1,FILTER(A2:D16,C2:C16="cancelled"),UNIQUE(CHOOSECOLS(query1,1,2,4))), 3, 1)
Level: hard