tSQL UNPIVOT of comma concatenated column into multiple rows - sql

Question

I have a table that has a value column. The value could be one value or it could be multiple values separated with a comma:
id | assess_id | question_key | item_value
---+-----------+--------------+-----------
1 | 859 | Cust_A_1 | 1,5
2 | 859 | Cust_B_1 | 2
I need to unpivot the data based on the item_value to look like this:
id | assess_id | question_key | item_value
---+-----------+--------------+-----------
1 | 859 | Cust_A_1 | 1
1 | 859 | Cust_A_1 | 5
2 | 859 | Cust_B_1 | 2
How does one do that in tSQL on SQL Server 2012?

Answer 1

We have a user defined function that we use for stuff like this that we called "split_delimiter":
CREATE FUNCTION [dbo].[split_delimiter](#delimited_string VARCHAR(8000), #delimiter_type CHAR(1))
RETURNS TABLE AS
RETURN
WITH cte10(num) AS
(
SELECT 1 UNION ALL SELECT 1 UNION ALL SELECT 1 UNION ALL
SELECT 1 UNION ALL SELECT 1 UNION ALL SELECT 1 UNION ALL
SELECT 1 UNION ALL SELECT 1 UNION ALL SELECT 1 UNION ALL SELECT 1
)
,cte100(num) AS
(
SELECT 1
FROM cte10 t1, cte10 t2
)
,cte10000(num) AS
(
SELECT 1
FROM cte100 t1, cte100 t2
)
,cte1(num) AS
(
SELECT TOP (ISNULL(DATALENGTH(#delimited_string),0)) ROW_NUMBER() OVER (ORDER BY (SELECT NULL))
FROM cte10000
)
,cte2(num) AS
(
SELECT 1
UNION ALL
SELECT t.num+1
FROM cte1 t
WHERE SUBSTRING(#delimited_string,t.num,1) = #delimiter_type
)
,cte3(num,[len]) AS
(
SELECT t.num
,ISNULL(NULLIF(CHARINDEX(#delimiter_type,#delimited_string,t.num),0)-t.num,8000)
FROM cte2 t
)
SELECT delimited_item_num = ROW_NUMBER() OVER(ORDER BY t.num)
,delimited_value = SUBSTRING(#delimited_string, t.num, t.[len])
FROM cte3 t;
GO
It will take a varchar value up to 8000 characters and will return a table with the delimited elements broken into rows. In your example, you'll want to use an outer apply to turn those delimited values into separate rows:
SELECT my_table.id, my_table.assess_id, question_key, my_table.delimited_items.item_value
FROM my_table
OUTER APPLY(
SELECT delimited_value AS item_value
FROM my_database.dbo.split_delimiter(my_table.item_value, ',')
) AS delimited_items