SQL Server 递归 CTE 和分页

Question

我有这张桌子

 CREATE TABLE [dbo].[friend_blocked_list](
 [subdomain] [varchar](50) NOT NULL,
 [un] [nvarchar](50) NOT NULL,
 [friend] [nvarchar](50) NOT NULL,
 [is_blocked] [bit] NOT NULL,
 [approved] [bit] NOT NULL)

我使用以下查询从中选择数据。选择查询结合了添加用户为好友的用户和已被用户添加为好友的用户

declare @un varchar(50), @subdomain varchar(50)

set @un='user2';
set @subdomain ='test.domain.com';

WITH FRIENDS as
(
  SELECT friend
  FROM friend_blocked_list
  WHERE un=@un and subdomain=@subdomain and approved=1 and is_blocked=0

  UNION ALL

  SELECT un as friend
  FROM friend_blocked_list
  WHERE friend=@un and subdomain=@subdomain and approved=1 and is_blocked=0
)
select friend from FRIENDS group by FRIENDS.friend order by FRIENDS.friend asc

它适用于少量数据，但我希望能够在服务器端进行分页以减少负载。我正在尝试将它与下面的分页 sp 结合起来

create PROCEDURE [dbo].[Paging]
    @subdomain varchar(50),
    @un varchar(50),
    @PageNumber int,
    @PageSize int
AS
BEGIN
   --paging
   DECLARE @FirstRow INT,@LastRow INT,@RowCount INT,@PageCount INT

   --find recordcount and pages
   SELECT @RowCount = COUNT(*), @PageCount = COUNT(*) / @PageSize 
   FROM friend_blocked_list 
   WHERE subdomain=@subdomain AND un=@un AND approved=1 AND is_blocked=0;

   --- calculate pages    
   IF @RowCount % @PageSize != 0 SET @PageCount = @PageCount + 1 
   IF @PageNumber < 1 SET @PageNumber = 1 
   IF @PageNumber > @PageCount SET @PageNumber = @PageCount 

   SELECT 
        CurrentPage = @PageNumber, 
        TotalPages = @PageCount, 
        TotalRows = @RowCount 

   -- mora calculation
   SELECT @FirstRow = ( @PageNumber - 1) * @PageSize + 1,
          @LastRow = (@PageNumber - 1) * @PageSize + @PageSize ;

   WITH MyTopics  AS
   (
      SELECT *, ROW_NUMBER() OVER (order by un asc) AS RowNumber
      FROM friend_blocked_list 
      WHERE subdomain=@subdomain AND un=@un AND approved=1 AND is_blocked=0
   )
   SELECT *
   FROM MyTopics
   WHERE RowNumber BETWEEN @FirstRow AND @LastRow
   ORDER BY RowNumber ASC;
end

但我总是遇到麻烦:)。主要问题是我的查询中的UNION ALL。它阻止我使用ROW_NUMBER() OVER。

有什么想法吗？

Answer 1

这是您为分页更新的过程：

CREATE PROCEDURE [dbo].[Paging]
  @subdomain varchar(50),
  @un varchar(50),
  @PageNumber int,
  @PageSize int
AS

  DECLARE @start_row int
  DECLARE @end_row int

  SET @end_row = @PageNumber * @PageSize
  SET @start_row = @end_row - (@PageSize - 1)

BEGIN

  WITH FRIENDS AS (
    SELECT t.friend
      FROM FRIEND_BLOCKED_LIST t
     WHERE t.un = @un 
       AND t.subdomain = @subdomain 
       AND t.approved = 1 
       AND t.is_blocked = 0
   UNION ALL
    SELECT t.un as friend
      FROM FRIEND_BLOCKED_LIST t
     WHERE t.friend = @un 
       AND t.subdomain = @subdomain 
       AND t.approved = 1 
       AND t.is_blocked = 0)
SELECT t.friend
  FROM (SELECT f.friend,
               ROW_NUMBER() OVER (ORDER BY f.friend) AS rownum
          FROM FRIENDS f
      GROUP BY f.friend) t
 WHERE t.rownum BETWEEN @start_row AND @end_row

END

如果您可以提供有关FRIEND_BLOCKED_LIST 表的更多信息，则可以将查询更改为使用一个 CTE。两个查询的UNION 具有相同的WHERE 子句同时区分两列让我想知道它是否不能写得更好。 FRIENDS CTE能否改写为：

SELECT COALESCE(t.un, t.friend) as friend
  FROM FRIEND_BLOCKED_LIST t
 WHERE @un = COALESCE(t.un, t.friend)
   AND t.subdomain = @subdomain 
   AND t.approved = 1 
   AND t.is_blocked = 0

Answer 2

将行号应用于要返回的列表：

WITH FRIENDS as
(
SELECT friend
  FROM friend_blocked_list
  WHERE un=@un and subdomain=@subdomain and approved=1 and is_blocked=0
UNION ALL
SELECT un as friend
  FROM friend_blocked_list
  WHERE friend=@un and subdomain=@subdomain and approved=1 and is_blocked=0 )
, recursive_friends as  (
select friend 
 , row_number() over (order by friend asc) as rn
from FRIENDS )
select friend 
  from recursive_friends
  where rn between @firstRow and @lastRow
  order by FRIENDS.friend asc;