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Pagination for retrieving large table records in SQL.

SQL

Pagination is a common technique used in web applications to display large sets of data in manageable chunks or pages. When dealing with a large dataset, retrieving all records at once is inefficient or not practical, especially if they won’t all be displayed on a single page.

To implement pagination in SQL, you need to retrieve a subset of records from the database based on the current page being requested and the number of records to display per page. This involves specifying the starting and ending rows for the desired page and then selecting only those rows from the database.

Here’s a breakdown of the implementation provided:

  • Parameters for Pagination: The implementation begins by declaring two parameters: @PageSize and @PageNumber. These parameters determine the number of records to display per page and the page number to retrieve, respectively.
  • Calculate Starting and Ending Rows: Using the formula (@PageNumber – 1) * @PageSize + 1, the starting row number for the desired page is calculated. The ending row number is then calculated by adding the page size to the starting row number and subtracting 1.
  • Common Table Expression (CTE): A common table expression (CTE) named PagedResults is defined. Inside this CTE, all columns from your_table are selected, and a row number is assigned to each row using the ROW_NUMBER() function. The row number is generated based on the specified ordering (in this case, [Your_Column]).
  • Main Query: The main query selects rows from the PagedResults CTE where the row number falls within the range of the desired page. This is achieved by filtering rows where the row number is between the calculated starting and ending row numbers.
-- Parameters for pagination
DECLARE @PageSize INT = 10; -- Number of records per page
DECLARE @PageNumber INT = 1; -- Page number to retrieve
-- Calculate the starting row number and ending row number for the desired page
DECLARE @StartRow INT = (@PageNumber - 1) * @PageSize + 1;
DECLARE @EndRow INT = @StartRow + @PageSize - 1;

-- Retrieve the records for the specified page
WITH PagedResults AS (
    SELECT 
        *,
        ROW_NUMBER() OVER (ORDER BY [Your_Column]) AS RowNumber
    FROM 
        your_table
)
SELECT 
    *
FROM 
    PagedResults
WHERE 
    RowNumber BETWEEN @StartRow AND @EndRow

Using this implementation, you can efficiently retrieve and display paginated data from a large table in your SQL database, which is particularly useful for building scalable web applications. Adjusting the values of @PageSize and @PageNumber allows you to navigate through the dataset and display different results pages.