Passing value in a function without quote T-SQL / SQL Server 2012? - sql-server

Question

I need assistance with a function in SQL Server 2012 that I created to check for the input value. If the functions detects a numeric - return 0, if detect character return 1.
But I get 2 different result for the same number passing it with quote and without quote.
select dbo.IS_ALIEN('56789')
returns 0
select dbo.IS_ALIEN(56789)
returns 1 (I need to return 0)
This is my function:
ALTER FUNCTION [dbo].[IS_ALIEN]
(#alienNAIC CHAR(1))
RETURNS NUMERIC(10,0)
AS
BEGIN
DECLARE #nNum NUMERIC(1,0);
BEGIN
SET #NnUM = ISNUMERIC(#alienNAIC)
END
BEGIN
IF #nNum = 1
RETURN 0;
END
RETURN 1;
END
Same concept for:
select dbo.IS_ALIEN('AA-11990043')
returns 1
or
select dbo.IS_ALIEN(NULL)
returns 1 (I need it to return 0)
I'm using Oracle function reference (below code is just reference from old database):
create or replace FUNCTION "IS_ALIEN"
( alienNAIC IN char )
RETURN NUMBER IS
nNum number;
BEGIN
SELECT MOD(alienNAIC, 2) into nNum FROM dual;
return 0;
EXCEPTION
WHEN INVALID_NUMBER THEN
return 1;
END;
But T-SQL function doesn't allow make exception of error. So I try to converted as much closer.

Answer 1

I suggest you use something like this (I've trimmed it down somewhat):
ALTER FUNCTION [dbo].[IS_ALIEN](#alienNAIC NVARCHAR(10))
RETURNS INT -- NOTE: You could also return tinyint or bit
AS
BEGIN
IF ISNUMERIC(#alienNAIC) = 1
RETURN 0;
RETURN 1;
END
The trouble with what you were trying is that there's an implicit cast to CHAR(1), the result of which is definitely not numeric as #Joel pointed out:
SELECT CAST(0 As CHAR(1)) -- returns character '0', ISNUMERIC(0) = 1
SELECT CAST(9 As CHAR(1)) -- returns character '9', ISNUMERIC(0) = 1
SELECT CAST(12345 As CHAR(1)) -- any number over 9 returns character '*', ISNUMERIC(12345) = 0
It's an odd implicit casting case I hadn't seen before. By making the parameter an NVARCHAR (assumes possible future double-byte input), strings will be correctly checked and integers passed in will be implicitly cast as NVARCHAR, and the ISNUMERIC check will succeed.
EDIT
Re-reading the question and comments, it looks like you want to identify a particular string syntax to determine if something is an "alien" or not. If you're comfortable changing business logic to fix what apparently is a poor legacy implementation, you could consider something like this instead:
ALTER FUNCTION [dbo].[temp](#alienNAIC NVARCHAR(10))
RETURNS INT -- NOTE: You could also return tinyint or bit
AS
BEGIN
IF #alienNAIC like 'AA-%' AND ISNUMERIC(RIGHT(#alienNAIC, LEN(#alienNAIC) - 3)) = 1
RETURN 1; -- notice this is now 1 instead of 0, we're doing a specific check for 'AA-nnnnn...'
RETURN 0;
END
Note that this should be thoroughly tested against legacy data if it's ever to interact with it - you never know what rubbish data a poorly written legacy system has left behind. Fixing this could well break other things. If you do make this change, document it well.

Answer 2

If you need to check just the first character then you can do like that:
CREATE FUNCTION [dbo].[IS_ALIEN]
(#alienNAIC VARCHAR(200))
RETURNS TINYINT
AS
BEGIN
IF LEFT(#alienNAIC,1) BETWEEN '0' AND '9' RETURN 1;
RETURN 0
END
GO

Answer 3

It seems like you are trying to check whether a string starts with a non-numeric character. Such pattern matches can be performed using LIKE, eg
declare #var nvarchar(10)='A56789'
select
case when #var LIKE '[0-9]%'
then 0 else 1
end AS IsAlien
Returns
1
Both declare #var nvarchar(10)=56789 and declare #var int=56789 return 0 because the number is implicitly converted to a string.
The expression is so short that you probably don't need to convert it to a function. If you do, it could be as simple as :
create FUNCTION [dbo].[IS_ALIEN] (#alienNAIC varchar(200))
RETURNS INT
begin
return case when #alienNAIC LIKE '[0-9]%'
then 0 else 1
end
end
If you want to perform the check in a WHERE clause, just use LIKE, not any function, eg:
WHERE alienNAIC NOT LIKE '[0-9]%'
This particular pattern is just a range search that covers all values between 0 and 9....... The server can use an index that covers the text column to quickly identify the matches. It can't do so when it has to check the result of a function. It will have to calculate the value for every single row before filtering.