How to validate string in SQL with characters - sql

Question

Check if the string is following the correct format or not. The correct format is as follows:
0000/00000. So far this is what i have got:
declare #ID nvarchar = '0000/00000'
SELECT (case when len(#id) not between 1 and 12 OR #id not like( '[0-9][0-9][0-9][0-9]' + '/' + '[0-9][0-9][0-9][0-9][0-9]')
OR LEFT(#id,13) LIKE '%[0-9]&' then 'OK' else 'ERROR' end

Answer 1

Why not just use not like?
where #id not like '[0-9][0-9][0-9][0-9]/[0-9][0-9][0-9][0-9][0-9]'
I assume that "0" means that any digit is allowed.

Answer 2

First, this will be a problem:
declare #ID nvarchar = '0000/00000'
This:
declare #ID nvarchar = '0000/00000';
SELECT #ID LEN(#ID), DATALENGTH(#ID);
Returns:
ID LEN
---- ----
0 1
With that in mind, note that this: PATINDEX({your pattern},#Id) will return a natural Boolean result.
DECLARE #ID1 NVARCHAR(1000) = '5555/12312',
#ID2 NVARCHAR(1000) = '1234/12345678',
#pattern VARCHAR(100) = '[0-9][0-9][0-9][0-9]/[0-9][0-9][0-9][0-9][0-9]';
SELECT IsCool = PATINDEX(#pattern,f.Id)
FROM (VALUES(#ID1),(#ID2)) AS f(Id);
Returns:
IsCool
-----------
1
0
If, by 0000/00000 you mean: Four digits + "/" + five digits then these expressions all work (note I made the pattern a variable for cleaner, easier to read code, it's not required):
DECLARE #ID NVARCHAR(1000) = '5555/12312',
#pattern VARCHAR(100) = '[0-9][0-9][0-9][0-9]/[0-9][0-9][0-9][0-9][0-9]';
SELECT CASE PATINDEX(#Pattern,#ID) WHEN 1 THEN 'Ok' ELSE 'Error' END;
SELECT IIF(PATINDEX(#Pattern,#ID)>0,'Ok','Error');
SELECT CHOOSE(PATINDEX(#Pattern,#ID)+1,'Error','Ok');
Your code suggests that #ID can be up to 12 characters long. Let's say, for example, the acceptable formats were:
0000/00000
0000/000000
0000/0000000
Then you could do this:
DECLARE #ID NVARCHAR(1000) = '5555/12312';
SELECT CASE WHEN LEN(#ID)<13 AND SIGN(PATINDEX('%[0-9][0-9]',#ID)) *
PATINDEX('[0-9][0-9][0-9][0-9]/[0-9][0-9][0-9][0-9][0-9]%',#ID) = 1
THEN 'Ok' ELSE 'Error' END;
Two final thoughts:
LEN({string}) can't be negative; LEN(#ID) < 13 will do the trick
If the max length is really 12 then make the parameter or variable NVARCHAR(13). This way, for example, someone passes in an 8000 character string, SQL doesn't have to scan the whole thing to determine that it's not valid.