UNPIVOT example in SQL Server

The PIVOT operator allows you to rotate, or pivot, data between columns and rows, and performs aggregations where they are required on any remaining column values. The UNPIVOT operator performs the reverse operation of PIVOT, by rotating columns into rows.

Note: PIVOT and UNPIVOT operators are available in SQL Server 2005 and onwards.

Here’s an example of using the UNPIVOT operator to convert repeating columns of a table, into a more normalized form

Sample Denormalized Table

CREATE TABLE #Student
(
StudentID int ,
Marks1 float,
Marks2 float,
Marks3 float
)

INSERT INTO #Student VALUES (1, 5.6, 7.3, 4.2)
INSERT INTO #Student VALUES (2, 4.8, 7.9, 6.5)
INSERT INTO #Student VALUES (3, 6.8, 6.6, 8.9)
INSERT INTO #Student VALUES (4, 8.2, 9.3, 9.1)
INSERT INTO #Student VALUES (5, 6.2, 5.4, 4.4)

SELECT * FROM #Student

OUTPUT

Unpivot Example

Let us know normalize this table using an UNPIVOT operator

Here’s the query to try out

SELECT StudentID, MarksNo, MarksRecd
FROM
(SELECT StudentID,
Marks1, Marks2, Marks3
FROM #Student) stu
UNPIVOT
(MarksRecd FOR MarksNo IN (Marks1, Marks2, Marks3)
) AS mrks

As you can see, we have declared two new columns here – MarksNo and MarksRecd. Here the column that will contain the column values (the ones that will be rotated like Marks1, Marks2,...) will be called MarksNo , and the column that will hold the values that currently reside under the rotated columns, will be called MarksRecd. This rotation of columns into rows is carried out by the UNPIVOT operator.

OUTPUT


About The Author

Suprotim Agarwal, MCSD, MCAD, MCDBA, MCSE, is the founder of DotNetCurry, DNC Magazine for Developers, SQLServerCurry and DevCurry. He has also authored a couple of books 51 Recipes using jQuery with ASP.NET Controls and a new one recently at The Absolutely Awesome jQuery CookBook.

Suprotim has received the prestigous Microsoft MVP award for nine times in a row now. In a professional capacity, he is the CEO of A2Z Knowledge Visuals Pvt Ltd, a digital group that represents premium web sites and digital publications comprising of Professional web, windows, mobile and cloud developers, technical managers, and architects.

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2 comments:

Shams Tarique said...

Very Nice tutorial for UNPIVOT

Unknown said...

Thank you so much!!! Simplified so that even I can pick this up!!!