Exclude where clause based on function specification - tsql

Question

I developed the following function:
create function kv_fn_ValuationPerItem_AW (#dDate date, #active bit)
returns table
as
return
(
select
Code ItemCode
, Description_1 ItemDescription
, ItemGroup
, Qty_On_Hand CurrentQtyOnHand
, AveUCst CurrentAvgCost
, Qty_On_Hand*AveUCst CurrentValue
from _bvSTTransactionsFull t
inner join StkItem s on t.AccountLink = s.StockLink
where ServiceItem = 0
and ItemActive = #active
and TxDate <= #dDate
group by Code, Description_1, ItemGroup, Qty_On_Hand, AveUCst
)
The function requires two parameters:
Date
Is the item Active - 1 = Active & 0 = Inactive
If I use the function as stipulated above, by specifying 1 for the Active Parameter, then the results will only be for Active Items.
If I specify 0, then it'll return all inactive Items.
How do I alter this function to cater for Active Items or both Active & Inactive?
i.e. if the parameter is 1, the where clause should read as ItemActive = #active, but when it's 0, the where clause should read as ItemActive in (1,0), How do I change the function to work like this?
I tried a case, but my syntax is not correct...

Answer 1

It's as simple as adding an or to your where cluase:
...
and (ItemActive = 1 OR #active = 0)
...
BTW, you might want to do it like this instead:
and (ItemActive = #active OR #active IS NULL)
which means that when you pass in 1 as #active you'll get only the active items, when you pass in 0 you'll get only the inactive members, but when you pass in null you'll get all records, regardless of the value in the ItemActive column.

Answer 2

Thanks Shnugo & Zohar for your answers,
Please amend your answers, then I'll mark yours as the answer.
The solution to my problem was to alter the Function as following:
create function kv_fn_ValuationPerItem_AW (#dDate date, #active bit)
returns table
as
return
(
select
Code ItemCode
, Description_1 ItemDescription
, ItemGroup
, Qty_On_Hand CurrentQtyOnHand
, AveUCst CurrentAvgCost
, Qty_On_Hand*AveUCst CurrentValue
from _bvSTTransactionsFull t
inner join StkItem s on t.AccountLink = s.StockLink
where ServiceItem = 0
and ItemActive in (1,#active)
and TxDate <= #dDate
group by Code, Description_1, ItemGroup, Qty_On_Hand, AveUCst
)

Answer 3

I think you are looking for this:
DECLARE #mockup TABLE(ID INT IDENTITY,SomeValue VARCHAR(100),Active BIT);
INSERT INTO #mockup VALUES('Row 1 is active',1)
,('Row 2 is active',1)
,('Row 3 is inactive',0)
,('Row 4 is inactive',0);
DECLARE #OnlyActive BIT=0; --set this to 1 to see active rows only
SELECT *
FROM #mockup m
WHERE (#OnlyActive=0 OR m.Active=1);
The idea is: If the parameter is set to 0 this expression is always true, if not, the column Active must be set to 1.
Hint: I used paranthesis, which was not needed in this simple case. But in your more complex WHERE clause they will be needed...
Hint2: I named the parameter OnlyActive, which expresses a bit better what you are looking for. You might turn the parameter to ShowAll with an invers logic too...