使用顶部和计数的最佳方法 - SQL 服务器 2008

Question

I have an 2008 C# application (back end SQL Server 2008) where sometimes queries return a large number of results. So, I researched some paging algorithms and put one in place that uses the TOP statement. I love the fact that if I have 500 total results and am only showing 20 results per page that I can only query the database for 20 records instead of storing all 500 records in memory.

The issue I have though is that in order to implement the paging algorithm, I need to know how many total records there are in this query. So, what I have done is to just run another query with the same parameters that just selects the ID (instead of the whole object) to try to make it run quickly. For some reason though, I think that running these two queries (thus establishing 2 connections) isn't the best approach.

So I need the count of all of the records but only want to select the limited number used in TOP. Would a temporary table be of use here? I have two different stored procedures now.

Thanks for any "best practices" advice anyone can give.

Answer 1

You could use object datasource...to implement this custom paging.

Answer 2

I would use ROW_NUMBER() OVER (ORDER BY...) . More details here .

Answer 3

I don't know what approach that you are taking for paging however the technique that I usually use is to use the ROW_NUMBER function, for example:

SELECT  Description, Date
FROM
(
    SELECT  ROW_NUMBER() OVER (ORDER BY Date DESC) AS Row,
        Description, Date 
    FROM Log
) AS LogWithRowNumbers
WHERE  Row >= 1 AND Row <= 10

This approach is the cleanest that I am aware of, works with any subquery and only requires a single query.

Of course if you wish to show a "total hits" or similar on your page then you will also need another query to get the row count:

SELECT COUNT(*) FROM Log

However you can execute both statements in the same batch to prevent the need for an extra "round trip" to the databse server.

Source - Paging Records Using SQL Server 2005 Database - ROW_NUMBER Function

Answer 4

If you perform both selects within your stored proceedure you would get two datatables in your dataset after using the Fill method.

Answer 5

I would try something like this:

;WITH CTE AS
(
    SELECT 
        ROW_NUMBER() OVER (ORDER BY Date DESC) AS Row,
        COUNT(*) OVER() AS TotalCount,
        Description, Date 
    FROM Log
)

SELECT *
FROM CTE
WHERE Row BETWEEN 1 AND 10

This will provide both paging and a count in 1 query. You could also use a CASE statement to only do the count at certain times. For instance does the count change while users are paging through?