How to transform SQL Server row data to columns? - sql-server

Question

I queried data like this
member_no cover_version product_id product_name product_type
--------- ------------- ---------- -------------------- ------------
11421 7 4 Excellent More E
11421 7 15 Comprehensive Data D
But I want to shape this data like this:
member_no cover_version product_e_id product_e_name product_d_id product_d_name
--------- ------------- ------------ -------------------- ------------ --------------------
11421 7 4 Excellent More 15 Comprehensive Data
I am using SQL Server 2008. What should be the best approach to shape the data as I want?

Answer 1

Assuming you've only got product types D and E as stated, a simple self-join will get you what you're after.
If you want something more generic, please expand your question.
DROP TABLE IF EXISTS #Demo
SELECT
*
INTO
#Demo
FROM
(VALUES
(11421, 7, 4, 'Excellent More', 'E')
,(11421, 7, 15, 'Comprehensive Data', 'D')) A
(member_no, cover_version, product_id, product_name, product_type)
SELECT
D.member_no
,D.cover_version
,E.product_id product_e_id
,E.product_name product_e_name
,D.product_id product_d_id
,D.product_name product_d_name
FROM
#Demo D
JOIN #Demo E ON D.member_no = E.member_no
AND D.product_type = 'D'
AND E.product_type = 'E';
member_no cover_version product_e_id product_e_name product_d_id product_d_name
----------- ------------- ------------ ------------------ ------------ ------------------
11421 7 4 Excellent More 15 Comprehensive Data

Answer 2

If you want to do this dynamically, based on unknown product types, you can use this.
DECLARE #SQL NVARCHAR(MAX),
#Columns NVARCHAR(MAX),
#CaseExpressions NVARCHAR(MAX) = 'MAX(CASE WHEN product_type = ''<<productType>>'' THEN product_id END) AS [product_<<productType>>_id],
MAX(CASE WHEN product_type = ''<<productType>>'' THEN product_name END) AS [product_<<productType>>_name]'
-- build concatenated string with 2 columns for each product_type in your table.
-- group by product_type to get distinct results.
-- replaces <<productType>> with the actual product_type value
SELECT #Columns = COALESCE(#Columns + ',', '') + REPLACE(#CaseExpressions, '<<productType>>', product_type)
FROM myTable
GROUP BY product_type
-- build select query
SET #SQL = 'SELECT member_no, cover_version,' + #Columns + ' FROM myTable GROUP BY member_no, cover_version'
-- to see what the dynamic sql looks like
PRINT #SQL
-- to execute the dynamic sql and see result
EXEC (#SQL)