Question

I’ve got the following working query:

        string sqlString =
            "SELECT  * " +
            "FROM (SELECT ROW_NUMBER() OVER (ORDER BY Id DESC) AS RowNum, * " +
            "FROM StreamView " +
            "WHERE Recipient = @Recipient " +
            ") AS RowConstrainedResult " +
            "WHERE RowNum >= @startAt " +
            "AND RowNum < @howMany " +
            "ORDER BY RowNum;";

Which then returns the proper rows given a startAt and howMany variables.
I would like to do the same with the query below:

        string sqlString =
        "SELECT DISTINCT l.* FROM Streams l " +
        "INNER JOIN Friendships f ON f.Sender = @UserName OR f.Recipient = @UserName " +
        "WHERE l.Sender <> @UserName AND l.Recipient <> @UserName AND ( " +
        "l.Sender = f.Recipient OR l.Sender = f.Sender OR " +
        "l.Recipient = f.Sender OR l.Recipient = f.Recipient) " +
        "ORDER BY DateTime DESC;";

The query above works perfectly, but i’d like to get ranges instead of all the available rows. I need the same functionality of the first query.

Ideas? thanks.

Answer 1

You should be able to put your original query in a subquery or a CTE and then select against that with a ROW_NUMBER() call. For example, something like (untested):

WITH CTE1 AS (
    SELECT DISTINCT
        l.*  -- List out all of the column names...
    FROM
    ...  -- Rest of your query, but you don't need the ORDER BY
),
CTE2 AS (
    SELECT
        CTE1.*,
        ROW_NUMBER() OVER (ORDER BY DateTime DESC) AS RowNum
    FROM
        CTE1
)
SELECT
    CTE2.*
FROM
    CTE2
WHERE
    RowNum BETWEEN @start_num and @end_num

I don’t know what kind of a query plan SQL Server would use for this though, so performance might not be very good.