Case and COLLATE SQL_Latin1_General_CP1_CI_AS in where statement - sql-server-2008

Question

I am working on a Stored Procedure that has two input parameters that I need to use COLLATE SQL_Latin1_General_CP1_CI_AS so that I can query non-case sensitive results; however, I would also like to allow for a Show All Option with the inputs. I have not found a way for the Collate to work in a case statement. Note: As a work around I will code with 4 different If statements for the different scenarios of choosing a value and/or show all, but would like something cleaner if possible. Current Code below
Declare
#INCo as bCompany,
#MatBeg as bMatl,
#MatEnd as bMatl,
#Catg as bGroup,
#Model as VarChar(20),
#PatternM as VarChar(20),
#SellOn as VarChar(20),
#PatternS as VarChar(20),
#ShowZero as bYN
set #INCo = '1'
set #MatBeg = '0'
set #MatEnd = 'ZZZZZZZZZZ'
set #Catg = '0'
set #Model = '637'
set #SellOn = 'EBAY'
set #ShowZero = 'Y'
begin
set #PatternM = '%' + #Model + '%';
set #PatternS = '%' + #SellOn + '%';
select i.INCo, i.Material, h.Description, h.Category, c.Description as CatgDesc, i.Booked as Quantity, i.PhyLoc, p.Storage,
i.udModelFit as FitsModel, i.udSellPriceNew as LikeNewSellPrice, i.udSellPriceUsed as UsedSellPrice, i.udSellingOn as SellingOn
from INMT i
left outer join HQMT h on i.MatlGroup=h.MatlGroup and i.Material=h.Material
left outer join HQMC c on h.MatlGroup=c.MatlGroup and h.Category=c.Category
left outer join udPhysicalloc p on i.PhyLoc=p.Physicalloc
where i.INCo = (CASE when #INCo <> 0 then #INCo else i.INCo END)
and i.Material >= #MatBeg and i.Material <= #MatEnd
and c.Category = (CASE when #Catg <> 0 then #Catg else c.Category END)
and i.udModelFit COLLATE SQL_Latin1_General_CP1_CI_AS like #PatternM
and i.udSellingOn COLLATE SQL_Latin1_General_CP1_CI_AS like #PatternS
and i.Booked >= (CASE when #ShowZero = 'N' then 1 else 0 END)
END
This code works works great if I only care about having non-case sensitive results for #Model and #SellOn. However, like the other parameters I have, I would like to include something that allows to show all results for that parameter. Something like:
i.udModelFit = (CASE when #Model <> 'ALL' then COLLATE SQL_Latin1_General_CP1_CI_AS like #PatternM else i.udModelFit END)
So as an example I would like to input #Model = 'ALL' and #SellOn = 'eBay' and results would be any Model with Sell On = EBAY (non-case sensitive)
Update: I was able to modify Where to the following and I am getting the desired results now.
where i.INCo = (CASE when #INCo <> 0 then #INCo else i.INCo END)
and i.Material >= #MatBeg and i.Material <= #MatEnd
and c.Category = (CASE when #Catg <> 0 then #Catg else c.Category END)
and (
(#Model IS NULL or i.udModelFit COLLATE SQL_Latin1_General_CP1_CI_AS like #PatternM)
or ((i.udModelFit like '%' or i.udModelFit IS NULL) and #Model = 'ALL')
)
and (
(#SellOn IS NULL or i.udSellingOn COLLATE SQL_Latin1_General_CP1_CI_AS like #PatternS)
or ((i.udSellingOn like '%' or i.udSellingOn IS NULL) and #SellOn = 'ALL')
)
and i.Booked >= (CASE when #ShowZero = 'N' then 1 else 0 END)

Answer 1

You can use and( (...) or (...) ) e.g.
and (#Model = 'ALL' or i.udModelFit like #PatternM SQL_Latin1_General_CP1_CI_AS)
If you want to toggle different search options based on input, you may want to consider writing your procedure using dynamic sql, and/or adding option (recompile).
Catch-all query reference:
Parameter Sniffing, Embedding, and the RECOMPILE Options - Paul White
Dynamic Search Conditions - Erland Sommarskog
Catch-all queries - Gail Shaw
An Updated "Kitchen Sink" Example - Aaron Bertand