SQL String join to table - sql

Question

Given few strings as
SET #Codes1 = 3,4
SET #Codes2 = 1
SET #Codes3 = --empty
Table -- TblCode
Id Code
1 A
2 B
3 C
4 D
How to convert the #Codes1, #Codes2, #Codes3 with join to the table TblCode so it returns the following output :
1. #Codes1 = CD
2. #Codes2 = A
3. #Codes3 = --empty
Note that the concatenation for the output is without the comma.
PS - This is a small example to a much larger and complex data set. Kindly ignore any wrongful design pattern here.

Answer 1

You can try this. I added the answer just for #Codes1, but it works with #Codes2 and #Codes3 too.
DECLARE #TblCode TABLE (Id INT, Code VARCHAR(2))
INSERT INTO #TblCode
VALUES(1, 'A'),
(2,'B'),
(3,'C'),
(4,'D')
DECLARE #Codes1 VARCHAR(10) = '3,4'
DECLARE #Codes2 VARCHAR(10) = '1'
DECLARE #Codes3 VARCHAR(10) = NULL
DECLARE #CodesOut VARCHAR(10) = ''
;WITH CTE_1 AS (
SELECT CODE= #Codes1 + ','
)
, CTE_2 AS -- It silit text to rows
(
SELECT RIGHT(CTE_1.CODE, LEN(CTE_1.CODE) - CHARINDEX(',',CTE_1.CODE)) CODE , SUBSTRING(CTE_1.CODE, 0, CHARINDEX(',',CTE_1.CODE)) ID, CHARINDEX(',',CTE_1.CODE) AS CI
FROM CTE_1
UNION ALL
SELECT RIGHT(CTE_2.CODE, LEN(CTE_2.CODE) - CHARINDEX(',',CTE_2.CODE)) CODE , SUBSTRING(CTE_2.CODE, 0, CHARINDEX(',',CTE_2.CODE)) ID, CHARINDEX(',',CTE_2.CODE) AS CI
FROM CTE_2 WHERE LEN(CTE_2.CODE) > 0
)
SELECT #CodesOut = #CodesOut + C.Code FROM CTE_2 INNER JOIN #TblCode C ON CTE_2.ID = C.Id
SELECT #CodesOut
Result:
CD

Answer 2

You can use a recursive CTE. Here is one method:
with c as (
select c.*, row_number() over (partition by id) as seqnum
from c
),
cte as (
select cast(#codes as varchar(max)) as str,
replace(#codes, id, code) as newstr,
1 as lev
from c
where seqnum = 1
union all
select str, replace(newstr, id, code), lev + 1
from cte join
c
on c.seqnum = cte.lev + 1
)
select top (1) newstr
from cte
order by lev desc;
If there is an error in the syntax, set up a SQL Fiddle or Rextester or something similar so it can be fixed.