How Can I Efficiently Select a Specific Range of Rows in SQL Server, Especially When Dealing with Large Datasets?

Selecting a Range of Rows in SQL Server: Managing Row Count Limitations

A common requirement in SQL Server is selecting a specific range of rows from a table. This can be achieved through çeşitli methods, each with its own limitations and performance considerations.

Limited Row Count in sys.all_columns

One technique involves using ROW_NUMBER() and CTEs to generate a list of rows within a specified range. However, this approach faces a limitation when applied to large tables, particularly for ranges exceeding 7374 rows. This is because the underlying sys.all_columns table has a有限数量的行。

Alternative Method for Generating a Range of Rows

To overcome this limitation, an alternative method utilizes cascaded CTEs to create a "Tally Table." This approach generates a list of numbers up to a specified range. Here's an example:

DECLARE @Range AS INT = 7374

;WITH E1(N) AS( -- 10 ^ 1 = 10 rows
    SELECT 1 FROM(VALUES (1),(1),(1),(1),(1),(1),(1),(1),(1),(1))t(N)
),
E2(N) AS(SELECT 1 FROM E1 a CROSS JOIN E1 b), -- 10 ^ 2 = 100 rows
E4(N) AS(SELECT 1 FROM E2 a CROSS JOIN E2 b), -- 10 ^ 4 = 10,000 rows
E8(N) AS(SELECT 1 FROM E4 a CROSS JOIN E4 b), -- 10 ^ 8 = 10,000,000 rows
CteTally(N) AS(
    SELECT TOP(@Range) ROW_NUMBER() OVER(ORDER BY(SELECT NULL))
    FROM E8
)
SELECT * FROM CteTally

This method creates a tally table up to the specified @Range, providing a more efficient way to generate a range of rows.

Performance Considerations

The performance of different methods for generating tally tables varies depending on the specific requirements and database environment. For a comprehensive performance comparison, refer to external resources such as Jeff Moden's article and other research studies.

Summary

Selecting a range of rows in SQL Server is a common task with various techniques available.Understanding the limitations and performance considerations of each approach enables the selection of the most efficient method for the specific scenario. The cascaded CTEs approach presented here offers a reliable and scalable way to generate a tally table up to a large number of rows, overcoming the limitations encountered in other methods.

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