Select string in between two strings - sql

Question

I need to output a string in between two strings. The problem is sometimes one of the two reference strings will be missing. If the first reference string is not missing and the second reference string is missing, I want to output from the first reference string to the end of the string. If the first reference string is missing, I want to output null or blank.
I saw a similar post but it included the reference strings. In my case, I do not want to include the reference strings.
SELECT SUBSTRING(#Text, CHARINDEX('1stRefStr', #Text)
, CHARINDEX('2ndRefStr',#text) - CHARINDEX('1stRefStr', #Text) + Len('2ndRefStr'))
Example:
Patient: A Date: 1/1/1 Message: Hi Message Sent To: B
1st string reference is "Message:"
2nd string reference is "Message Sent To:"
Expected Result:
Hi

Answer 1

If you don't mind a helper function.
Being a TVF, it is easy to incorporate into a CROSS APPLY if your data is in a table.
I modified a split/parse function to accept two non-like delimeters.
Example
Declare #Text varchar(max) = 'Patient: A Date: 1/1/1 Message: Hi Message Sent To: B'
Select *
From [dbo].[tvf-Str-Extract](#Text,'Message:','Message Sent') A
Returns
RetSeq RetVal
1 Hi
The Function
CREATE FUNCTION [dbo].[tvf-Str-Extract] (#String varchar(max),#Delim1 varchar(100),#Delim2 varchar(100))
Returns Table
As
Return (
Select RetSeq = row_number() over (order by RetSeq)
,RetVal = left(RetVal,charindex(#Delim2,RetVal)-1)
From (
Select RetSeq = row_number() over (order by 1/0)
,RetVal = ltrim(rtrim(B.i.value('(./text())[1]', 'varchar(max)')))
From ( values (convert(xml,'<x>' + replace((Select replace(#String,#Delim1,'§§Split§§') as [*] For XML Path('')),'§§Split§§','</x><x>')+'</x>').query('.'))) as A(XMLData)
Cross Apply XMLData.nodes('x') AS B(i)
) C1
Where charindex(#Delim2,RetVal)>1
)
Update As A CROSS APPLY
Declare #YourTable table (ID int,SomeCol varchar(max))
Insert Into #YourTable values
(1,'Patient: A Date: 1/1/1 Message: Hi Message Sent To: B')
Select A.ID
,B.*
From #YourTable A
Cross Apply (
Select RetSeq = row_number() over (order by RetSeq)
,RetVal = left(RetVal,charindex('Message Sent',RetVal)-1)
From (
Select RetSeq = row_number() over (order by 1/0)
,RetVal = ltrim(rtrim(B.i.value('(./text())[1]', 'varchar(max)')))
From ( values (convert(xml,'<x>' + replace((Select replace(SomeCol,'Message:','§§Split§§') as [*] For XML Path('')),'§§Split§§','</x><x>')+'</x>').query('.'))) as A(XMLData)
Cross Apply XMLData.nodes('x') AS B(i)
) C1
Where charindex('Message Sent',RetVal)>1
) B