How Can I Pivot Data in SQL Server 2000 to Transform Row-Based Data into a Column-Based Format?

Pivoting Data in SQL Server 2000: A Detailed Explanation

SQL Server 2000 provides a powerful feature called pivoting that enables users to transform data from a row-based format to a column-based format. This can be useful for scenarios where you need to summarize data across multiple columns or create a matrix view of the data.

Problem Statement:

In one particular instance, a user has two tables:

• Products: Contains basic product information such as ProductId and Name.
• Product Meta: Stores product metadata with columns such as MetaKey and MetaValue.

The user requires a result set that pivots the MetaValue column from the Product Meta table based on the MetaKey column, with the ProductId and Name columns from the Products table as row headers.

Optimal Solution:

To achieve this transformation, you can use the following SQL query:

SELECT P.ProductId, P.Name
    , MIN(CASE WHEN PM.MetaKey = 'A' THEN PM.MetaValue END) AS A
    , MIN(CASE WHEN PM.MetaKey = 'B' THEN PM.MetaValue END) AS B
    , MIN(CASE WHEN PM.MetaKey = 'C' THEN PM.MetaValue END) AS C
FROM Products AS P
JOIN ProductMeta AS PM
    ON PM.ProductId = P.ProductId
GROUP BY P.ProductId, P.Name

Explanation:

• The SELECT clause specifies the columns to be included in the result set.
• The MIN() aggregate function is used to return the minimum value for each MetaKey within each group of ProductId and Name.
• The CASE expression is used to determine which column (A, B, or C) to populate based on the MetaKey value.
• The GROUP BY clause specifies the columns that define the rows in the result set.

Note:

Using a GROUP BY clause is essential in this scenario to ensure that the rows are grouped correctly. Failing to use a GROUP BY clause would result in a staggered result. Additionally, each column not included in the GROUP BY clause must be wrapped in an aggregate function (in this case, MIN()).

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