Function to check value and returns result - sql-server

Question

I need to create function in SQL to check data in variables or parameters as below
#Category as varchar(50)='ABC,DEF'
#Value as varchar(50)='1,2'
And compare #Category value with Category in table then return value matching from parameter
JOB TABLE ---
JOB CATEGORY
123 ABC
234 DEF
234 SSS
Select JobNo,FUNCTION(#Category,#Value,CATEGORY) from JOB
FINAL RESULTS
JOB VALUE
123 1
234 2
234 0
If category match then return value from parameter else return 0.

Answer 1

If you can't use a static lookup table as mentioned in the comments (for example, perhaps the mapping needs to be dynamic based on data supplied by the application), then this looks like a job for a table valued parameter.
Right now you have two parameters, but it seems to me that the values in the parameters are related. That is to say, right now you have #category = 'ABC,DEF' and #value = '1,2', but I think you intend each "element" in the comma delimited set of "categories" to associate with the "element" in the comma delimiited set of "values" that is in the same position.
Right now the design is brittle, because what would happen if I use parameters like this: #category = 'ABC,DEF,GHI,JKL', #value = '1'?
So, you can make your code more durable, and use the sort of "join-based" lookup table solution being recommended to you in the comments, by using a function that takes a table valued parameter argument. To do this, you first have to create the table valued parameter as a type in your database. We then accept a parameter of that type, and join onto it. In the solution below I have "guessed" at datatypes for category and value that seem reasonable based on the sample data in your question.
Also, I've kept the "structure" of your solution - ie, the function is written in such a way that it can be "applied" against every row in jobs, individually. We don't have to do it this way. We could instead just do the whole query inside the function (ie, including the join to the job table), but perhaps you want to use the function against other tables that also have a cateogry column? I won't try to second guess the overall design here. But I will switch the function to an inline table valued function (which returns one row with one column) rather than a scalar function, for performance reasons.
-- schema and data to match your question
create table dbo.job (job int, category char(3));
insert dbo.job(job, category) values (123, 'ABC'), (234, 'DEF'), (234, 'SSS');
go
-- solution
create type dbo.CategoryValues as table
(
category char(3) unique,
[value] int
);
go
create or alter function dbo.MapCategory(#category char(3), #map dbo.CategoryValues readonly)
returns table as return
(
select [value] from #map where category = #category
);
go
-- to call the function we need to pass a parameter of type
-- dbo.CategoryValues with the mappings we desire
declare #map dbo.CategoryValues;
insert #map values ('ABC', 1), ('DEF', 2)
-- outer apply the function to each row in the job table.
select j.job, [value] = isnull(v.[value], 0)
from dbo.job j
outer apply dbo.MapCategory(j.category, #map) v