如何引用一个 CTE 两次？

Question

我有一个非常胖的公用表表达式，其中包括行号，以便我可以返回分页结果集。我还想在分页结果集之前返回与查询匹配的记录总数。

with recs as (select *, row_number() over (order by id) as rownum from ......)
select * from recs where rownum between @a and @b .... select count(*) from recs

显然我上面的查询是不完整的，但这只是为了说明我的观点。我想要一页结果和匹配的总数。我如何做到这一点，而不必从字面上复制和粘贴整个 20 多行 CTE？

Answer 1

这就是我们在生产环境中处理分页（暂时没有会话管理）的方式。按预期执行。

DECLARE
   @p_PageNumberRequested  int = 1,
      -- Provide -1 to retreive all pages with all the rows.
   @p_RowsPerPage          int = 25

;WITH Numbered AS (
SELECT
   ROW_NUMBER() OVER (ORDER BY YourOrdering) AbsoluteRowNumber
,  COUNT(1) OVER () TotalRows
,  YourColumns
FROM
   YourTable
),
Paged AS (
SELECT
   (AbsoluteRowNumber - 1) / @p_RowsPerPage + 1 PageNumber,
   *
FROM
   Numbered)
SELECT
   ROW_NUMBER() OVER(PARTITION BY PageNumber ORDER BY AbsoluteRowNumber) RowNumberOnPage,
   *
FROM
   Paged
WHERE
      PageNumber = @p_PageNumberRequested
   OR
      @p_PageNumberRequested = -1
ORDER BY 
   AbsoluteRowNumber

Answer 2

这是最好的：

;WITH recs AS
(SELECT a,b,c,
      row_number() over (
                         ORDER BY id) AS RowNum,
                   row_number() over () AS RecordCount
FROM ......)
SELECT a,b,c,rownum,RecordCount FROM recs
WHERE rownum BETWEEN @a AND @b

Answer 3

您可以附加一个包含总行数的字段，当然它会在每一行上

select recs.*,totalrows = (select count(0) from recs) 
from recs

Answer 4

您可以使用逗号创建多个引用上述 CTE 的 CTE。

只是为了说明我的意思：

with recs as (
select 
    *, 
    row_number() over (order by id) as rownum from ......
    ),
counts as (
    select count(*) as totalrows from recs
)
select recs.*,count.totalrows
from recs
cross apply counts 
where rownum between @a and @b .... 

这不是一个好的解决方案。

this article 中描述了在 CTE 中计算总计数而不计算记录的最佳解决方案。

DECLARE @startRow INT; SET @startrow = 50;
WITH cols
AS
(
    SELECT table_name, column_name, 
        ROW_NUMBER() OVER(ORDER BY table_name, column_name) AS seq, 
        ROW_NUMBER() OVER(ORDER BY table_name DESC, column_name desc) AS totrows
    FROM [INFORMATION_SCHEMA].columns
)
SELECT table_name, column_name, totrows + seq -1 as TotRows
FROM cols
WHERE seq BETWEEN @startRow AND @startRow + 49
ORDERBY seq

Answer 5

不要以为你可以。来自MSDN

公用表表达式 (CTE) 可以是 被认为是一个临时的结果集 在执行中定义的 单个 SELECT、INSERT 的范围， 更新、删除或创建视图 声明。

强调“单个 SELECT、INSERT、UPDATE、DELETE 或 CREATE VIEW 语句”。

这可能是您想要使用Temporary Table 的情况。

CREATE TABLE #Recs
{
  .....
}
INSERT INTO #Recs
select *, row_number() over (order by id) as rownum from ......

如果你事先不知道表的结构，你可以使用这个表格来创建一个临时表：

select *, row_number() over (order by id) as rownum INTO #Recs from ......

您将能够按照上述方式使用临时表。