Question

select tmp.id, tmp.portfolio,
   ROW_NUMBER() OVER(order by tmp.id DESC) AS RowNum 
from 
  (select r.portfolio, r.id
   from research r 
   where r.created_by = 'Adam Cohen'
 ) as tmp 
WHERE RowNum BETWEEN 5 AND 10;

我无法在where条件中引用RowNum，因为它显示无效的列名称＆＃39; RowNum＆＃39;。请帮助我使用正确的语法来获得结果。

修改 - 更改要求

SELECT * FROM 
( 
     select id, portfolio, 
     CASE WHEN l.posted_on IS NULL 
          THEN CONVERT(VARCHAR(40),l.created_on,120) 
          ELSE CONVERT(VARCHAR(40),l.posted_on,120) 
     END AS sort_by, 
     ROW_NUMBER() OVER(order by sort_by DESC) AS RowNum 
     from research 
     where created_by = 'Adam Cohen' 
) x 
WHERE x.RowNum BETWEEN 5 AND 10

我尝试添加上述Row_Number功能，但我将sort_by视为无效列。

Answer 1

您需要将投影包装在派生表中，尽管您可以删除内部tmp表：

SELECT * FROM
(
    select id, portfolio,
       ROW_NUMBER() OVER(order by id DESC) AS RowNum 
    from 
       research
    where created_by = 'Adam Cohen'
) x
WHERE x.RowNum BETWEEN 5 AND 10

修改

请注意，如果您在最终选择中实际上不需要伪行号，那么从Sql 2012开始，在您的“数据页面”场景中，您将能够使用OFFSET FETCH来应用根本需要ROW_NUMBER()或派生表：

select id, portfolio from research where created_by = 'Adam Cohen' order by id desc offset 5 rows fetch next 6 rows only;

编辑＃2，重新提出新要求

CASE WHEN l.posted_on IS NULL THEN CONVERT(VARCHAR(40),l.created_on,120) ELSE CONVERT(VARCHAR(40),l.posted_on,120) END AS sort_by

可以更简洁地表达为

CONVERT(VARCHAR(40), COALESCE(posted_on, created_on)) AS AS sort_by

但是，如果您仍然需要原始行号，则还要在窗口函数ORDER BY（OVER）中使用此投影，为了干掉它，您将需要嵌套的派生表。但是，您仍然可以使用SQL 2012 OFFSET / FETCH NEXT进行分页：

SELECT *, ROW_NUMBER() OVER(order by sort_by DESC) AS RowNum FROM ( SELECT id, portfolio, CONVERT(VARCHAR(40), COALESCE(posted_on, created_on)) AS sort_by from research where created_by = 'Adam Cohen' ) y ORDER BY id DESC OFFSET 5 ROWS FETCH NEXT 6 ROWS ONLY;

Answer 2

您需要将ROW_NUMBER嵌套在派生表中：

select tmp.id, tmp.portfolio, tmp.RowNum
from 
  (select r.portfolio, r.id,
      ROW_NUMBER() OVER(order by r.id DESC) AS RowNum 
   from research r 
   where r.created_by = 'Adam Cohen'
 ) as tmp 
WHERE RowNum BETWEEN 5 AND 10;

Row_Number函数中的Sql Server别名

2 个答案: