UNPIVOTing Data with T-SQL

Disclaimer: I imported this post from WordPress to Jekyll on 9/2/23. Forgive the misformatting until I get a chance to clean it up.

Requirement

I had a data set (pricing by state) delivered last week from a business application user that I needed to import into the application’s database. The user provided an Excel worksheet in the format below:

SKU	TN	MS	AR
1	.99	.89	.89
2	1.09	.99	.99
3	.99	1.09	.99

My database table, however, was designed as follows:

Sku	State	Price
4	TN	.89
4	MS	.99
4	AR	1.09
5	TN	.89
5	AR	1.09
5	MS	.99

I needed a plan to transform the worksheet data to match my table’s structure.

A Solution

First, I imported the data from the Excel workbook directly into a new table ([tmpPrices]) using the SSMS Import and Export Wizard.

Then, I could INSERT INTO SELECT from the imported table using the query below. The UNPIVOT operator rotates the [State] column identifiers into row values that align with a particular [SKU]. The column specified before the UNPIVOT operator ([Price]) is the one that holds the values that are currently under the columns being rotated. The column that will contain the column values that I rotated follows the operator ([State]).

INSERT INTO [Prices]
([Sku],
[State],
[Price]
)
SELECT [SKU],
[State],
[Price]
FROM
(
SELECT [SKU],
[AR],
[MS],
[TN]
FROM [tmpPrices]
) p UNPIVOT([Price] FOR [State] IN([AR],
[MS],
[TN])) unpvt;

via Microsoft