Comma Delimited Result set + SQL Query - sql-server-2008

Question

I got two tables with data as listed below:
Table1: Student
Table2: Subject
I need the output as:
I got this acheived with below query using for XML PATH
Code:
WITH cte
AS ( SELECT Stu.Student_Id ,
Stu.Student_Name ,
( SELECT Sub.[Subject] + ','
FROM [Subject] AS Sub
WHERE Sub.Student_Id = Stu.Student_Id
ORDER BY Sub.[Subject]
FOR
XML PATH('')
) AS [Subjects]
FROM dbo.Student AS Stu
)
SELECT Student_id [Student Id] ,
student_name [Student Name] ,
SUBSTRING(Subjects, 1, ( LEN(Subjects) - 1 )) AS [Student Subjects]
FROM cte
My question is there a better way to do this without using XML Path?

Answer 1

This is a very good approach and has become pretty well accepted. There are several approaches and this blog post describes a lot of them.
One interesting approach that exists is using the CLR to do the work for you which will significantly reduce the complexity of the query with the trade-off of running external code. Here is a sample of what the class might look like in the assembly.
using System;
using System.Collections.Generic;
using System.Data.SqlTypes;
using System.IO;
using Microsoft.SqlServer.Server;
[Serializable]
[SqlUserDefinedAggregate(Format.UserDefined, MaxByteSize=8000)]
public struct strconcat : IBinarySerialize{
private List values;
public void Init() {
this.values = new List();
}
public void Accumulate(SqlString value) {
this.values.Add(value.Value);
}
public void Merge(strconcat value) {
this.values.AddRange(value.values.ToArray());
}
public SqlString Terminate() {
return new SqlString(string.Join(", ", this.values.ToArray()));
}
public void Read(BinaryReader r) {
int itemCount = r.ReadInt32();
this.values = new List(itemCount);
for (int i = 0; i <= itemCount - 1; i++) {
this.values.Add(r.ReadString());
}
}
public void Write(BinaryWriter w) {
w.Write(this.values.Count);
foreach (string s in this.values) {
w.Write(s);
}
}
}
And that would net a query a bit more like this.
SELECT CategoryId,
dbo.strconcat(ProductName)
FROM Products
GROUP BY CategoryId ;
Which is quite a bit simpler obviously. Take it for what it's worth :)
Good day!