Question

Can I assign a list of strings to a variable for use in an IN statement without using Dynamic SQL?

I am developing a report in SSRS which allows the user to select one of three possible values as a parameter which in turn will assign values associated with that choice to an IN statement. Some parameters have a single value associated and some have several.

Cases 1 and 2 run properly, but case 3 does not because it is passed as a scalar value instead of a list. I have tried various ways of escaping the quotes around each item, but it does not work.

declare @items as varchar(50)
set @items =
  CASE @parameter
    WHEN 1 then 'first'
    WHEN 2 then 'second'
    WHEN 3 then 'third, fourth'
  END

select column1
from table1
where column1 IN (@items)

Answer 1

No, you can not. You can use table variable in following way:

DECLARE @table TABLE(item varchar(50))

IF @parameter = 3
BEGIN 
   INSERT INTO @table(item) VALUES ('third'), ('fourth')
END
ELSE
 BEGIN
   INSERT INTO @table VALUES(
     CASE @parameter      
        WHEN 1 then 'first'
       WHEN 2 then 'second'
     END 
    )
 END

-- And use IN(subquery)
SELECT column1     
FROM table1     
WHERE column1 IN (SELECT item FROM @table) 

Also you can use EXISTS which much faster in such condition checks but you won’t get significant performance improvements due to a small items cound (1-2)

SELECT column1     
FROM table1 t
WHERE EXISTS (SELECT * FROM @table WHERE item = t.column1)