Is there a better way to parse value into multiple columns? - tsql

Question

I have a value that needs to be parsed into a potential three values:
MasterUnit
Unit1
Unit2
Unit3
10ABC
10A
10B
10C
10AB
10A
10B
NULL
I'm accomplishing what I need in the below script. My question to you... Is there a better, more efficient way to do so (in fewer lines of code)?
cast([UnitNum] as char(5)) as MasterUnit,
left(cast([UnitNum] as char(5)), 3) as Unit1,
case
when (left(left(cast([UnitNum] as char(5)), 2) + right(cast([UnitNum] as char(5)), 2),3)) = left(cast([UnitNum] as char(5)), 2)
then NULL
else (left(left(cast([UnitNum] as char(5)), 2) + right(cast([UnitNum] as char(5)), 2),3))
end as Unit2,
case
when (left(cast([UnitNum] as char(5)), 2)) + (right(cast([UnitNum] as char(5)), 1)) = left([UnitNum],2)
then NULL
else (left(cast([UnitNum] as char(5)), 2) + right(cast([UnitNum] as char(5)), 1))
end as Unit3

Answer 1

With a little bit of string manipulation and a CROSS APPLY
Select A.*
,Unit1 = S1+nullif(substring(S2,1,1),'')
,Unit2 = S1+nullif(substring(S2,2,1),'')
,Unit3 = S1+nullif(substring(S2,3,1),'')
From YourTable A
Cross Apply ( values ( left(MasterUnit,patindex('%[^0-9]%',MasterUnit)-1),substring(MasterUnit,patindex('%[^0-9]%',MasterUnit),100) ) ) B(S1,S2)
Reults

Answer 2

Making some assumptions about your sample data, perhaps something like the following using a cross apply to re-use the initial two characters is about as minimal as possible :
select MasterUnit,
u + NullIf(Substring(MasterUnit,3,1),'') Unit1,
u + NullIf(substring(MasterUnit,4,1),'') Unit2,
u + NullIf(substring(MasterUnit,5,1),'') Unit3
from t
cross apply(values(Left(MasterUnit,2)))m(u);