Splitting out string, using the results to lookup reference, then returning the reference name as a string?

Question

I have a field that contains a comma separated string of sys_id’s that relate to another table.
I am trying to write a query that returns the name value from the reference table, so that the result is a comma separated string of the name field.
Can anyone help with the SQL required to split out the sys_id’s, do the look-up and return the names back into a string?
Table1
Number
Category
1001
Sys_id1, Sys_id3, Sys_id9
1002
Sys_id3
1003
Sys_id4,Sys_3
1004
Sys_id1, Sys_id9, Sys_id10, Sys_id6
Category Reference Table
Category Sys_id
Category_Name
Sys_id1
Consulting
Sys_id3
Negotiate
Sys_id4
Planning
Sys_id6
Building
Sys_id9
Receipt
Sys_id10
Complete
The result I am looking for would be.
Number
Category
1001
Consulting, Negotiate, Receipt
1002
Negotiate
1003
Planning, Negotiate
1004
Consulting, Receipt, Complete, Building

Answer 1

I am not going to arguee regarding your model, but you should consider normalizing it.
The idea is to have a function to split the string and return a row for each element in the list. Dump the result into a table and then use FOR XML PATH to do the string aggregation.
To learn about different methods you could use to create the split function refer to this article.
Arrays and Lists in SQL Server
http://www.sommarskog.se/arrays-in-sql.html
Here is an example using XML methods. This is just an example and it doesn't deal with proper indexing, weird characters as part of the list that can't be translated as xml, etc.
SET NOCOUNT ON;
USE tempdb;
GO
DECLARE @T TABLE (
Number int,
Category varchar(50)
INSERT INTO @T (Number, Category)
VALUES
(1001, 'Sys_id1, Sys_id3, Sys_id9'),
(1002, 'Sys_id3'),
(1003, 'Sys_id4, Sys_id3'),
(1004, 'Sys_id1, Sys_id9, Sys_id10, Sys_id6');
DECLARE @R TABLE (
Sys_id varchar(15),
Category_Name varchar(35)
INSERT INTO @R (Sys_id, Category_Name)
VALUES
('Sys_id1', 'Consulting'),
('Sys_id3', 'Negotiate'),
('Sys_id4', 'Planning'),
('Sys_id6', 'Building'),
('Sys_id9', 'Receipt'),
('Sys_id10', ' Complete');
DECLARE @W TABLE (
Number int,
pos int,
Sys_id varchar(15),
PRIMARY KEY (Number, Sys_id)
INSERT INTO @W (Number, pos, Sys_id)
SELECT
A.Number,
ROW_NUMBER() OVER(PARTITION BY A.Number ORDER BY N.x) AS pos,
N.x.value('(text())[1]', 'varchar(15)') AS Sys_id
FROM
@T AS A
CROSS APPLY
(SELECT A.Category AS [text()] FOR XML PATH('')) AS B(c)
CROSS APPLY
(SELECT CAST('<l>' + REPLACE(B.c, ', ', '</l><l>') + '</l>' AS xml)) AS C(x)
CROSS APPLY
C.x.nodes('/l') AS N(x);
SELECT
A.Number,
STUFF(
SELECT
', ' + C.Category_Name
FROM
@W AS B
INNER JOIN
@R AS C
ON C.Sys_id = B.Sys_id
WHERE
B.Number = A.Number
ORDER BY
B.pos
FOR XML PATH(''), TYPE
).value('(text())[1]', 'varchar(MAX)'), 1, 2, '') AS Category
FROM
@T AS A;
GO
AMB
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