Rows in their own columns depending on their value

Question

I have a select query that currently produces the following results:

Description   Code    Price
 Product 1     A        5
 Product 1     B        4
 Product 1     C        2

Using the following query:

SELECT DISTINCT np.Description, p.promotionalCode, p.Price
FROM            Price AS p INNER JOIN
                         nProduct AS np ON p.nProduct = np.Id

I want to produce the following:

Description  A  B  C
 Product 1   5  4  2

Which database product are you using? – Martin Oct 25 '08 at 11:04 — Martin, Oct 25 '08 at 11:04

score 6 · Accepted Answer · answered Oct 25 '08 at 11:27

SELECT 
    np.Id, 
    np.Description, 
    MIN(Case promotionalCode WHEN 'A' THEN Price ELSE NULL END) AS 'A',
    MIN(Case promotionalCode WHEN 'B' THEN Price ELSE NULL END) AS 'B',
    MIN(Case promotionalCode WHEN 'C' THEN Price ELSE NULL END) AS 'C'
FROM 
    Price AS p 
INNER JOIN nProduct AS np ON p.nProduct = np.Id
GROUP BY 
    np.Id,
    np.Description

Here is a simple test example:

DECLARE @temp TABLE (
    id INT,
    description varchar(50),
    promotionalCode char(1),
    Price smallmoney
)

INSERT INTO @temp
select 1, 'Product 1', 'A', 5
    union
SELECT 1, 'Product 1',  'B', 4
    union
SELECT 1, 'Product 1', 'C', 2



SELECT
    id,
    description,
    MIN(Case promotionalCode WHEN 'A' THEN Price ELSE NULL END) AS 'A',
    MIN(Case promotionalCode WHEN 'B' THEN Price ELSE NULL END) AS 'B',
    MIN(Case promotionalCode WHEN 'C' THEN Price ELSE NULL END) AS 'C'
FROM
     @temp
GROUP BY 
    id,
    description

You're relying on knowing that the values are A, B, and C. If there are many promotional codes, this SQL will become quite difficult to maintain. And the questioner is retrieving those values from the database. — DOK, Oct 25 '08 at 15:21

score 2 · Answer 2 · answered Oct 25 '08 at 14:06

If you're using SQL Server 2005, you can use the new PIVOT operator.

Simple PIVOT -- the number of orders a customer places for individual products.

Structure of a simple Order table:

CREATE TABLE Sales.[Order]
    (Customer varchar(8), Product varchar(5), Quantity int)

The table contains the following values:

Customer Product Quantity
    Mike     Bike    3
    Mike     Chain   2
    Mike     Bike    5
    Lisa     Bike    3
    Lisa     Chain   3
    Lisa     Chain   4

Ex: a PIVOT operation on the Order table:

SELECT *
    FROM Sales.[Order]
    PIVOT (SUM(Quantity) FOR Product IN ([Bike],[Chain])) AS PVT

The expected output from this query is:

Customer Bike Chain
Lisa        3    7
Mike        8    2

If you aren't using SQL Server, you might search for "pivot" for your database.

score 1 · Answer 3 · answered Oct 25 '08 at 12:05

Duckworth's answer is good. If you can get more than one value for each cell, you might want to use AVG or SUM instead of MIN, depending on what you want to see.

If your DBMS supports it, you might also want to look into a Crosstab query, or a pivot query. For example, MS Access has crosstab queries.

Rows in their own columns depending on their value

3 Answers3