SQL unpivot of multiple columns - sql-server

Question

I would like the following wide table to be unpivotted but only where a user has a true value against the field, along with the appropriate date.
Current State:
CUSTOMER_ID
First_Party_Email
Third_Party_Email
First_Party_Email_Date
Third_Party_Email_Date
40011111
1
1
2021-01-22 04:38:00.000
2021-01-17 06:38:00.000
50022222
NULL
1
NULL
2021-01-18 04:38:00.000
80066666
1
NULL
2021-01-24 05:38:00.000
NULL
_______________
_______________________
_______________________
_______________________________
_______________________________
Required State:
Customer_ID
Type
Value
Date
40011111
First_Party_Email
1
22/01/2021 04:38
40011111
Third_Party_Email
1
17/01/2021 06:38
50022222
Third_Party_Email
1
18/01/2021 04:38
80066666
First_Party_Email
1
24/01/2021 05:38
_______________________________________________________________________
Associated query to create table and my attempt that doesn't work:
create table Permissions_Obtained
(Customer_ID bigint
,First_Party_Email bit
,Third_Party_Email bit
,First_Party_Email_Date datetime
,Third_Party_Email_Date datetime
)
insert into Permissions_Obtained
(Customer_ID
,First_Party_Email
,Third_Party_Email
,First_Party_Email_Date
,Third_Party_Email_Date
)
VALUES
(40011111, 1, 1, '2021-01-22 04:38', '2021-01-17 06:38'),
(50022222, NULL, 1, NULL, '2021-01-18 04:38'),
(80066666, 1, NULL, '2021-01-24 05:38', null)
select *
from Permissions_Obtained
select
customer_id, Permission
from Permissions_Obtained
unpivot
(
GivenPermission
for Permission in (
First_Party_Email, Third_Party_Email
)
) unpiv1,
unpivot
(
GivenPermissionDate
for PermissionDate in (
First_Party_Email_Date, Third_Party_Email_Date
)
) unpiv2
where GivenPermission = 1
--drop table Permissions_Obtained
Any help would be massively appreciated. TIA

Answer 1

You cannot have multiple unpivots at the same time. Instead you can use Cross Apply or Inner join or union, union all or kind of joins depending on your requirement. I have added a sample answer for this using join and unpivot.
SELECT
unpvt.Customer_ID
, [Type]
, ISNULL(po.First_Party_Email ,po.Third_Party_Email) AS [Value]
,CASE WHEN unpvt.Type = 'First_Party_Email' THEN po.First_Party_Email_Date
ELSE po.Third_Party_Email_Date
END AS [Date]
FROM
(
SELECT
Customer_ID, First_Party_Email , Third_Party_Email
FROM Permissions_Obtained
) p
UNPIVOT
( [Value] FOR [Type] IN
(First_Party_Email , Third_Party_Email )
)AS unpvt
INNER JOIN Permissions_Obtained [po]
on [po].Customer_ID = unpvt.Customer_ID

Answer 2

When un-pivoting multiple columns, CROSS APPLY (VALUES is often the easiest and most effective solution.
It creates a virtual table per-row of the previous table, and therefore un-pivots it into separate rows.
SELECT
p.Customer_Id,
v.[Type],
v.Value,
v.Date
FROM Permissions_Obtained p
CROSS APPLY (VALUES
('First_Party_Email', p.First_Party_Email, p.First_Party_Email_Date),
('Third_Party_Email', p.Third_Party_Email, p.Third_Party_Email_Date)
) v([Type], Value, Date)
where v.Value IS NOT NULL;