How to pass udtt individually to another function in SQL - sql

Question

Suppose I want to get student summaries from a two tables: student, grade:
CREATE PROCEDURE prc_get_student_grade_summaries
#studentIds [Integer_udtt] READONLY
AS
BEGIN
SELECT Name,
func_GetGradeAForStudent()
FROM tbl_student AS tS
INNER JOIN
#studentIds AS tSI
ON tS.Id = tSI.studentId
Integer udtt is defined as this:
CREATE TYPE [Integer_udtt] AS TABLE (
[Id] INT NOT NULL,
PRIMARY KEY CLUSTERED ([Id] ASC));
func_GetGradeAForStudent is something like select COUNT(*) from student where studentId = id AND grade = 1 -- 1: A
The result I want is list of summary:
StudentId Number of A
101 5
102 4
103 2
What is the correct way to pass in the studentId from #studentIds to the func_GetGradeAForStudent?

Answer 1

You can't pass table-value parameters to UDF's:
MSDN:
Limitations of Table-Valued Parameters
There are several limitations to table-valued parameters:
You cannot pass table-valued parameters to user-defined functions.
Table-valued parameters can only be indexed to support UNIQUE or PRIMARY KEY constraints. SQL Server does not maintain statistics on
table-valued parameters.
Table-valued parameters are read-only in Transact-SQL code. You cannot update the column values in the rows of a table-valued
parameter and you cannot insert or delete rows. To modify the data
that is passed to a stored procedure or parameterized statement in
table-valued parameter, you must insert the data into a temporary
table or into a table variable.
You cannot use ALTER TABLE statements to modify the design of table-valued parameters.
Since these are just a list of student Ids, one possibility would be to pass those Ids as a comma-separeted list of ids and use a split function to recreate a table from the comma-separeted list. There's a ton of examples here on SO and elsewhere where you can find sample implementation of a split function.
Or even better, do everything inside your proc. I don't really see the need for that function if all is doing is a select count(*)... You should be able to do everything inline, perhaps using a subselect as so:
CREATE PROCEDURE prc_get_student_grade_summaries
#studentIds [Integer_udtt] READONLY
AS
BEGIN
SELECT Name,
(select COUNT(*) from student where studentId = tSI.studentId AND grade = 1 ) as NumberOfAs
FROM tbl_student AS tS
INNER JOIN
#studentIds AS tSI
ON tS.Id = tSI.studentId
UPDATE
Sample split function that takes a comma-separated list and returns a table:
CREATE FUNCTION [dbo].[fnSplit](
#sInputList VARCHAR(8000) -- List of delimited items
, #sDelimiter VARCHAR(8000) = ',' -- delimiter that separates items
) RETURNS #List TABLE (item VARCHAR(8000))
BEGIN
DECLARE #sItem VARCHAR(8000)
WHILE CHARINDEX(#sDelimiter,#sInputList,0) <> 0
BEGIN
SELECT
#sItem=RTRIM(LTRIM(SUBSTRING(#sInputList,1,CHARINDEX(#sDelimiter,#sInputList,0)-1))),
#sInputList=RTRIM(LTRIM(SUBSTRING(#sInputList,CHARINDEX(#sDelimiter,#sInputList,0)+LEN(#sDelimiter),LEN(#sInputList))))
IF LEN(#sItem) > 0
INSERT INTO #List SELECT #sItem
END
IF LEN(#sInputList) > 0
INSERT INTO #List SELECT #sInputList -- Put the last item in
RETURN
END
And you call it like this: select * from fnSplit(#CommaSeparetedList,',');