How to Dynamically Pivot Data in SQL Server

 

SQL is the lifeblood of any data professional. If you can’t leverage SQL and you work with data, your life will be more difficult than it needs to be.

In this video I am using SQL Server Express to turn a simple normalized dataset into a pivoted dataset. This is not a beginner video as I assume you are familiar with basic SQL concepts.

T-SQL is Microsoft’s SQL language that contains additional functions and capabilities over and above ANSI standards. We’ll use some of these functions to turn the following data set that displays average rents in major American cities into a pivoted denormalized dataset.

The City values in the City column will become individual columns in a new pivoted dataset with their respective Average Rent values appearing underneath.

We’re going to transform this:

Normalized Data

Into this:

Pivoted Data

Notice how the city values are now column heads and the respective Average Rent values are underneath.

Make sure you watch the video but here is the code used in the example.

IF OBJECT_ID('tempdb..##TBL_TEMP') IS NOT NULL
DROP TABLE ##TBL_TEMP

--This parameter will hold the dynamically created SQL script
DECLARE   @SQLQuery AS NVARCHAR(MAX)

--This parameter will hold the Pivoted Column values
DECLARE   @PivotColumns AS NVARCHAR(MAX)

SELECT   @PivotColumns= COALESCE(@PivotColumns + ',','') + QUOTENAME([City])
FROM [dbo].[tbl_Rent]

/* UNCOMMENT TO SEE THE NEW COLUMN NAMES THAT WILL BE CREATED */
--SELECT   @PivotColumns

--Create the dynamic query with all the values for
--pivot column at runtime
--LIST ALL FILEDS EXCEPT PIVOT COLUMN

SET   @SQLQuery =
   N'SELECT [City Code],[Metro],[County],[State],[Population Rank],' +   @PivotColumns + '
   INTO ##TBL_TEMP
   FROM [dbo].[tbl_Rent]
   
   PIVOT( MAX([Average Rent])
      FOR [City] IN (' + @PivotColumns + ')) AS Q'

/* UNCOMMENT TO SEE THE DYNAMICALLY CREATED SQL STATEMENT */
--SELECT   @SQLQuery
--Execute dynamic query
EXEC sp_executesql @SQLQuery

/* VIEW PIVOTED TABLE RESULTS */
Select * from ##TBL_TEMP

 

Big shoutout to StackOverflow for help with this example.

 

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