Sql Pivot convert 2 columns into rows - sql

Question

I have a StockLines table in MsSql 2017. It has columns:
Product, QuantityInStock, ReservedQuantity.
CocaCola 50 20
Now I need to display that info in 2 rows:
Product Quantity Reserved
CocaCola 20 true
CocaCola 30 false
Is it possible to achive using Pivot()? Am I on a correct path?
P.S I'm using Entity Framework Core.

Answer 1

You can easily do this using apply:
select t.product, v.quantity, v.reserved
from t cross apply
(values (t.ReservedQuantity, 'true'),
(t.QuantityInStock - t.ReservedQuantity, 'false')
) v(quantity, reserved);
I think you could do this using unpivot, but that is superfluous syntax. apply implements lateral joins, which are very powerful. This is just one example of how they can be used.

Answer 2

A simple to understand approach would be UNION:
SELECT product, reservedquantity as quantity, 'true' as reserved FROM stocklines
UNION ALL
SELECT product, quantityinstock-reservedquantity, 'false' FROM stocklines
I am wondering though if you have other lines in the table, detailing other reservations of the same product, are they also supposed to come from the total? Is the stock quantity the same across all lines? Hopefully all individual reservations of products are grouped together so stock lines table contains one row per product (or things get messy)
You also mentioned you're using ef core- see https://learn.microsoft.com/en-us/ef/core/querying/raw-sql
This technique could also be modified into a LINQ statement, perhaps something like(untested):
context.StockLines.Select(s => new[] { new {
s.Product,
Quantity = s.QuantityInStock - s.ReservedQuantity,
Reserved = false
},
new {
s.Product,
Quantity = s.ReservedQuantity,
Reserved = true
}
}).SelectMany().ToList()
The idea being we take each record and split it into an anonymous type representing the reserved and a type representing the unreserved as an array output from the first select then use selectmany to flatten the enumerable-of-arrays-of-type to an enunerable-of-type
This latter solution might need some tweaks; totally untested

Answer 3

You can use UNPIVOT
SELECT Product,
Quantity,
CASE Reserved
WHEN 'QuantityInStock' THEN 'FALSE'
ELSE 'TRUE'
END AS Reserved
FROM pro
UNPIVOT(
Quantity FOR Reserved IN (QuantityInStock, ReservedQuantity)
) AS t
Another way is without CASE operator, but with subquery and aliases:
SELECT Product,
Quantity,
Reserved
FROM (
SELECT product,
QuantityInStock AS [false],
ReservedQuantity AS [true]
FROM pro
) AS tt
UNPIVOT(Quantity FOR Reserved IN ([false], [true])) upvt