How to Implement SQL Server 2008 Pagination Using ROW_NUMBER()?

How to Use ROW_NUMBER() for Pagination in SQL Server 2008

Pagination, a technique for dividing large result sets into manageable pages, is essential for efficient data retrieval. SQL Server 2008 offers several methods for pagination, one of which is using the ROW_NUMBER() function.

ROW_NUMBER() Function

ROW_NUMBER() is a window function that generates a unique sequential number for each row in a result set, based on a specified ordering.

Syntax:

ROW_NUMBER() OVER (PARTITION BY partition_expression ORDER BY order_expression)

• partition_expression: Divides the result set into groups.
• order_expression: Specifies the order in which the rows should be numbered.

Usage for Pagination

To use ROW_NUMBER() for pagination, you can create a common table expression (CTE) as follows:

WITH CTEResults AS
(
    SELECT IDColumn, SomeField, DateField, ROW_NUMBER() OVER (ORDER BY DateField) AS RowNum
    FROM MyTable
)

This CTE assigns a sequential number (RowNum) to each row in the MyTable, ordered by the DateField.

To retrieve a specific page, you can then filter the CTE:

SELECT * 
FROM CTEResults
WHERE RowNum BETWEEN @PageNumber * @PageSize AND (@PageNumber + 1) * @PageSize;

In this query, @PageNumber represents the desired page number, and @PageSize is the number of rows per page. For example, to retrieve the second page of 10 rows each, you would use:

SELECT * 
FROM CTEResults
WHERE RowNum BETWEEN 10 AND 20;

Benefits of Using ROW_NUMBER()

• Transparent ordering: ROW_NUMBER() handles the ordering internally, eliminating the need for explicit ORDER BY clauses in the main query.
• Efficient for large result sets: ROW_NUMBER() only performs the ordering once, making it suitable for large result sets.
• Supports complex ordering: ROW_NUMBER() allows for complex ordering expressions, including multiple columns and partition by clauses.

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