Recursive scalar function - sql

Question

I'm attempting to rebuild some VBA functions in SQL server 2016 and I'm having difficult making a recursive function work properly.
My attempt below is returning NULL and when I step through the function in debug #returnValue never seems to hold a value even though it appears to recurse correctly.
Can someone please advise how to fix this.
Example expected results:
select [dbo].TickDiff(1.01, 1.05) -- Expect result 4
select [dbo].TickDiff(2.02, 16) -- Expect result 121
Functions:
CREATE FUNCTION [dbo].TickDiff (#odds1 float, #odds2 float)
RETURNS float
AS
BEGIN
DECLARE #returnValue as float
IF (#odds1 > #odds2)
BEGIN
set #returnValue = #returnValue + [dbo].TickDiff([dbo].TicksDown(#odds1), #odds2) + 1
END
ELSE
IF (#odds1 < #odds2)
BEGIN
set #returnValue = #returnValue + [dbo].TickDiff([dbo].TicksUp(#odds1), #odds2) + 1
END
RETURN #returnValue;
END
GO
CREATE FUNCTION [dbo].TicksUp(
#odds float
)
RETURNS float
AS
BEGIN
RETURN
case
when #odds < 1 then 1.02
when #odds >= 1 and #odds <= 1.99 then #odds + 0.01
when #odds >= 2 and #odds <= 2.98 then #odds + 0.02
when #odds >= 3 and #odds <= 3.95 then #odds + 0.05
when #odds >= 4 and #odds <= 5.9 then #odds + 0.1
when #odds >= 6 and #odds <= 9.8 then #odds + 0.2
when #odds >= 10 and #odds <= 19.5 then #odds + 0.5
when #odds >= 20 and #odds <= 29 then #odds + 1.0
when #odds >= 30 and #odds <= 48 then #odds + 2.0
when #odds >= 50 and #odds <= 95 then #odds + 5.0
when #odds >= 100 and #odds < 1000 then #odds + 10
when #odds >= 1000 then 1000
end
END
GO
CREATE FUNCTION [dbo].TicksDown(
#odds float
)
RETURNS float
AS
BEGIN
RETURN
case
when #odds <= 1.01 then 1.01
when #odds >= 1.01 and #odds <= 2 then #odds - 0.01
when #odds >= 2.02 and #odds <= 3 then #odds - 0.02
when #odds >= 3.05 and #odds <= 4 then #odds - 0.05
when #odds >= 4.1 and #odds <= 6 then #odds - 0.1
when #odds >= 6.2 and #odds <= 10 then #odds - 0.2
when #odds >= 10.5 and #odds <= 20 then #odds - 0.5
when #odds >= 21 and #odds <= 30 then #odds - 1.0
when #odds >= 32 and #odds <= 50 then #odds - 2.0
when #odds >= 55 and #odds <= 100 then #odds - 5.0
when #odds >= 110 and #odds < 1000 then #odds - 10
when #odds >= 1000 then 990
end
END
GO
The VBA functions I'm trying to copy are below:
Function TicksDown(ByVal odds As Currency) As Currency
Dim IncrementOdds As Currency
Select Case odds
Case 1.01 To 2
IncrementOdds = 0.01
Case 2.02 To 3
IncrementOdds = 0.02
Case 3.05 To 4
IncrementOdds = 0.05
Case 4.1 To 6
IncrementOdds = 0.1
Case 6.2 To 10
IncrementOdds = 0.2
Case 10.5 To 20
IncrementOdds = 0.5
Case 21 To 30
IncrementOdds = 1
Case 32 To 50
IncrementOdds = 2
Case 55 To 100
IncrementOdds = 5
Case 110 To 1000
IncrementOdds = 10
End Select
If Math.Round(odds - IncrementOdds, 2) >= 1.01 Then
TicksDown = Math.Round(odds - IncrementOdds, 2)
Else
TicksDown = 1.01
End If
End Function
Function TicksUp(ByVal odds As Currency) As Currency
Dim IncrementOdds As Currency
Select Case odds
Case 1 To 1.99
IncrementOdds = 0.01
Case 2 To 2.98
IncrementOdds = 0.02
Case 3 To 3.95
IncrementOdds = 0.05
Case 4 To 5.9
IncrementOdds = 0.1
Case 6 To 9.8
IncrementOdds = 0.2
Case 10 To 19.5
IncrementOdds = 0.5
Case 20 To 29
IncrementOdds = 1
Case 30 To 48
IncrementOdds = 2
Case 50 To 95
IncrementOdds = 5
Case 100 To 1000
IncrementOdds = 10
End Select
If Math.Round(odds + IncrementOdds, 2) <= 1000 Then
TicksUp = Math.Round(odds + IncrementOdds, 2)
Else
TicksUp = 1000
End If
End Function
Function TickDiff(odds1 As Currency, odds2 As Currency) As Long
If odds1 > odds2 Then
odds1 = TicksDown(odds1)
TickDiff = TickDiff(odds1, odds2) + 1
ElseIf odds1 < odds2 Then
odds1 = TicksUp(odds1)
TickDiff = TickDiff(odds1, odds2) + 1
Else
'Found, Exit Recursive Function
End If
End Function

Answer 1

You need to set your #ReturnValue to zero:
DECLARE #returnValue as float = 0.0
That being said, your second example exceeds SQLs max recursion of 32. You may want to rewrite without recursion. Here's an example: http://www.sql-server-helper.com/error-messages/msg-217.aspx

Answer 2

Your #returnValue is not initialized , so it is null. And
set #returnValue = #returnValue + [dbo].TickDiff([dbo].TicksDown(#odds1), #odds2) + 1
evaluates to null.
Try
CREATE FUNCTION [dbo].TickDiff (#odds1 float, #odds2 float)
RETURNS float
AS
BEGIN
DECLARE #returnValue as float = 0.;
IF (#odds1 > #odds2)
BEGIN
set #returnValue = #returnValue + [dbo].TickDiff([dbo].TicksDown(#odds1), #odds2) + 1
END
ELSE
IF (#odds1 < #odds2)
BEGIN
set #returnValue = #returnValue + [dbo].TickDiff([dbo].TicksUp(#odds1), #odds2) + 1
END
RETURN #returnValue;
END
Also case expressions can be simplified because sql-server evaluates when conditions in the order specified.
CREATE FUNCTION [dbo].TicksUp(
#odds float
)
RETURNS float
AS
BEGIN
RETURN
case
when #odds < 1 then 1.02
when #odds <= 1.99 then #odds + 0.01
when #odds <= 2.98 then #odds + 0.02
when #odds <= 3.95 then #odds + 0.05
when #odds <= 5.9 then #odds + 0.1
when #odds <= 9.8 then #odds + 0.2
when #odds <= 19.5 then #odds + 0.5
when #odds <= 29 then #odds + 1.0
when #odds <= 48 then #odds + 2.0
when #odds <= 95 then #odds + 5.0
when #odds < 1000 then #odds + 10
when #odds >= 1000 then 1000
end
END