SQL select from a Case when generated field - sql

Question

In my query there's this field is generated by this statement
CASE WHEN T1.unitMsr='MT' then STR((T1.Quantity),12,5)
ELSE STR((T1.Quantity*T2.NumInSale),12,5)END as OrderQty,
isnull(str(sum(CASE WHEN TN.unitMsr = 'MT'
Then TN.Quantity ELSE TN.Quantity*T2.NumInSale END),8,5),'0.00000') as DO_Qty_MT,
before the select statement ends, i would like to achieve something like this
Case When DO_Qty_MT >= OrderQty Then 'Normal'
Else 'Abnormal' END
As 'Closing method'
How should i substitute DO_Qty_MT and OrderQty with proper referencing?

Answer 1

The typical ways to add in such "variables" is to use a CTE or subquery. An alternative is a lateral join, which SQL Server supports with the apply keyword:
select . . ., v.OrderQty,
coalesce(str(sum(case when TN.unitMsr = 'MT'
then TN.Quantity
else TN.Quantity * T2.NumInSale
end), 8, 5
), '0.00000'
) as DO_Qty_MT,
from . . . outer apply
(values (case when T1.unitMsr = 'MT' then str(T1.Quantity, 12, 5)
else str(T1.Quantity * T2.NumInSale, 12, 5)
end)
) v(OrderQty)
This makes it simpler to do chains of calculations.
Also, I don't understand why you are using str(). Decimal/numeric would seem to do what you want -- and keep the representation of the value as a number not a string.

Answer 2

It seems to me that you are setting the order as "abnormal" if total order quantity is less than any of the order rows..
But this is possible only when T1.Quantity or T2.NumInSale are NULL or negative (when OrderQty<0).
Starting from you TN table you can simply test rows using:
-- get all rows with detailed information and Normal/Abnormal test..
select
*, Case When isnull(OrderQty, -1)<0 Then 'Abnormal' Else 'Normal' END As [Closing method]
from TN
Even simpler if you need only "Abnormal" rows
select *, 'Abnormal' As [Closing method]
from TN
where isnull(OrderQty, -1)<0
If you just want to extract Orders with abnormal rows use distinct YourOrderId instead of * in previous queries.
-- get all orders with Normal/Abnormal test
select distinct OrderId,
Case When isnull(OrderQty, -1)<0 Then 'Abnormal' Else 'Normal' END As [Closing method]
from TN
-- get only Abnormal orders
select distinct OrderId, 'Abnormal' As [Closing method]
from TN
where isnull(OrderQty, -1)<0