String split column and join to another table

Question

Let\'s say I have 2 tables like this :

Job Offers:

+----+------------+------------+
| ID |    Name    | Categories |
+----+--------         


        

Answer 1

If you can live with one row per category then this will work:

select jo.*, c.name as category
from joboffers jo join
     categories c
     on ',' + jo.categories + ',' like '%,' + cast(c.id) + ',%';

Re-aggregating them into a string is painful in SQL Server (but very possible).

Note: you have a really, really bad data structure. So you should fix it as mentioned in a comment. Why is it bad?

• You are storing numbers as strings.
• You have ids that don't have a foreign key relationship to the reference table.
• You are storing multiple values in a single field.

Answer 2

From SQL SERVER 2016 we can use sql inbuilt function STRING_SPLIT as below :

SELECT * FROM JobOffers as j 
outer apply STRING_SPLIT(j.[Categories], ',') s
left join dbo.Categories as c on c.CategoryID =s.value

Answer 3

You can greatly simplify this to something like this.

SELECT
    O.[ID]                  AS OfferID,
    O.[Name]                AS OfferName,
    c.[CategoryName]      AS CategoryName,
    c.[CategoryID]        AS CategoryID
FROM
    JobOffers AS O
outer apply [dbo].[Split](O.[Categories], ',') s
left join Categories as C on c.CategoryID = s.Items

The concern I have is your splitter. If there is more than a single select statement the performance is going to suffer horribly. For a good explanation of various splitters available you can visit this article.

http://sqlperformance.com/2012/07/t-sql-queries/split-strings