Operand type clash: varchar is incompatible with User-Defined Table Type - sql

Question

I created a User-Defined Table Type:
CREATE TYPE dbo.ListTableType AS TABLE(
ITEM varchar(500) NULL
)
I leverage it in a function:
CREATE FUNCTION dbo.fn_list_to_string
(
#LIST dbo.ListTableType READONLY
)
RETURNS varchar(max)
AS
BEGIN
DECLARE #RESULT varchar(max)
SET #RESULT = ''
DECLARE #NL AS CHAR(2) = CHAR(13) + CHAR(10)
SELECT #RESULT = #RESULT + ITEM + #NL FROM #LIST
SET #RESULT = SUBSTRING(#RESULT, 1, LEN(#RESULT) - 1)
RETURN #RESULT
END
Finally, I try to use this function in a simple select:
SELECT
P.PROGRAM_ID,
PROGRAM_NAME,
PROGRAM_DESC,
P.STATUS_ID,
STATUS_DESC,
P.CONTACT_SID,
I.FIRST_NAME + ' ' + I.LAST_NAME as CONTACT_NAME,
P.CLARITY_ID,
dbo.fn_list_to_string(
( SELECT CONVERT(varchar,CLARITY_ID) as ITEM
FROM dbo.MUSEUM_PROGRAM_PROJECTS as A
JOIN dbo.MUSEUM_PROJECTS as B on B.PROJECT_ID = A.PROJECT_ID
WHERE PROGRAM_ID = P.PROGRAM_ID )
) as PROJECT_CLARITY_IDS
FROM dbo.MUSEUM_PROGRAMS as P
LEFT JOIN dbo.MUSEUM_PROGRAM_STATUS_TYPES as S on S.STATUS_ID = P.STATUS_ID
LEFT JOIN dbo.v_IDVAULT_ENRICHED_CURRENT_EMPLOYEES as I on I.[SID] = P.CONTACT_SID
But I get this error:
Operand type clash: varchar is incompatible with ListTableType
Any idea why? Also if there's another [more elegant] way to achieve what I'm trying to do I'm open to suggestions as well! Thanks in advance!

Answer 1

Here is a simple demonstration of the FOR XML PATH technique which does all of this with a very simple subquery and no table types or extremely inefficient multi-statement table-valued functions etc.
USE tempdb;
GO
CREATE TABLE dbo.P(Program_ID INT);
CREATE TABLE dbo.M(Clarity_ID INT, Program_ID INT);
INSERT dbo.P VALUES(1),(2),(3),(4);
INSERT dbo.M VALUES(1,1),(1,2),(2,3),(3,2),(1,4),(4,1);
SELECT
P.PROGRAM_ID,
PROJECT_CLARITY_IDS = STUFF((
SELECT CHAR(13)+CHAR(10)+CONVERT(VARCHAR(12),Clarity_ID)
FROM dbo.M WHERE Program_ID = p.Program_ID
FOR XML PATH(''), TYPE).value('.[1]','nvarchar(max)'),1,2,'')
FROM dbo.P AS p;
SQLfiddle demo
The output doesn't look right in SQLfiddle or in results to grid in Management Studio, because they strip out carriage returns/line feeds for display purposes, but you can replace CHAR(13)+CHAR(10) with two commas or semi-colons or something to verify that there are two characters there.

Answer 2

Using STUFF..FOR XML PATH construct for concatanation in combination with CTE will get the results you'd like. Something like this:
WITH CTE_PROJECT_CLARITIES AS
(
SELECT DISTINCT PROGRAM_ID
, STUFF((
SELECT CHAR(13) + CHAR(10) + CONVERT(varchar(11),CLARITY_ID)
FROM dbo.MUSEUM_PROGRAM_PROJECTS as A
JOIN dbo.MUSEUM_PROJECTS as B on B.PROJECT_ID = A.PROJECT_ID
WHERE A.PROGRAM_ID = X.PROGRAM_ID
FOR XML PATH ('')),1,2,'') AS PROJECT_CLARITY_IDS
FROM MUSEUM_PROGRAM_PROJECTS X
)
SELECT
P.PROGRAM_ID,
PROGRAM_NAME,
PROGRAM_DESC,
P.STATUS_ID,
STATUS_DESC,
P.CONTACT_SID,
I.FIRST_NAME + ' ' + I.LAST_NAME as CONTACT_NAME,
P.CLARITY_ID,
X.PROJECT_CLARITY_IDS
FROM dbo.MUSEUM_PROGRAMS as P
LEFT JOIN dbo.MUSEUM_PROGRAM_STATUS_TYPES as S on S.STATUS_ID = P.STATUS_ID
LEFT JOIN dbo.v_IDVAULT_ENRICHED_CURRENT_EMPLOYEES as I on I.[SID] = P.CONTACT_SID
LEFT JOIN CTE_PROJECT_CLARITIES X ON X.PROGRAM_ID = p.PROGRAM_ID
SQLFiddle DEMO (not sure if I got the columns right, but you'll get the idea)