SQL是否在现有查询中获取单个值？

我有一个返回一堆行的查询。 但使用相同的查询，我想：

1。获取表中的总行数
2。获取认证用户名所在的行号

现在我是这样做的：

BEGIN
 DECLARE @startRowIndex INT;
 DECLARE  @PageIndex INT;
 DECLARE  @RowsPerPage INT;

 SET @PageIndex = 0;
 SET @RowsPerPage = 15;
 SET @startRowIndex = (@PageIndex * @RowsPerPage) + 1;

 WITH messageentries
      AS (SELECT   Row_number()
                  OVER(ORDER BY score DESC) AS row,
                Count(DISTINCT town.townid) AS towns,
                user_details.username,
                user_score.score,
                allience.alliencename,
                allience.allienceid,
                allience.alliencetagname,
                (SELECT Count(* ) FROM   user_details) AS numberofrows
       FROM     user_details
                INNER JOIN user_score
                  ON user_details.username = user_score.username
                INNER JOIN town
                  ON user_details.username = town.townownername
                LEFT OUTER JOIN allience_roles
                  ON user_details.useralliencerole = allience_roles.roleid
                LEFT OUTER JOIN allience
                  ON allience_roles.allienceid = allience.allienceid
       GROUP BY user_details.username,
                user_score.score,
                allience.alliencename,
                allience.allienceid,
                allience.alliencetagname)
 SELECT *, (SELECT row FROM messageentries WHERE username = 'myUsername') AS myself
 FROM   messageentries
 WHERE  row BETWEEN @startRowIndex AND @StartRowIndex + @RowsPerPage - 1
END 

这是可行的，但这两个嵌套的选择不是对表中的每一行运行一次吗/

    ...
  (SELECT Count(* ) FROM   user_details) AS numberofrows
    ...
  (SELECT row FROM messageentries WHERE username = 'myUsername') AS myself

所以我的问题是，我如何才能得到我想要的值，尽可能“低成本”，最好是在同一个查询中

提前感谢：）

试试这个

DECLARE @NumberOfRows INT

SELECT @NumberOfRows = Count(* ) FROM   user_details
 WITH messageentries
      AS (SELECT   Row_number()
                  OVER(ORDER BY score DESC) AS row,
                Count(DISTINCT town.townid) AS towns,
                user_details.username,
                user_score.score,
                allience.alliencename,
                allience.allienceid,
                allience.alliencetagname,
                @NumberOfRows AS numberofrows
       FROM     user_details
                INNER JOIN user_score
                  ON user_details.username = user_score.username
                INNER JOIN town
                  ON user_details.username = town.townownername
                LEFT OUTER JOIN allience_roles
                  ON user_details.useralliencerole = allience_roles.roleid
                LEFT OUTER JOIN allience
                  ON allience_roles.allienceid = allience.allienceid
       GROUP BY user_details.username,
                user_score.score,
                allience.alliencename,
                allience.allienceid,
                allience.alliencetagname)
 SELECT *, MyRowNumber.row AS myself
 FROM   messageentries,
        (SELECT row FROM messageentries WHERE username = 'myUsername') MyRowNumber
 WHERE  row BETWEEN @startRowIndex AND @StartRowIndex + @RowsPerPage - 1

这一个将被缓存（很可能在

工作表中具体化）

对于这一个，很可能会构建一个
惰性假脱机
（或
急切假脱机
），用于提取此值。
是的，它可以工作，但不知何故，如果我像我一样编写SELECT*，MyRowNumber.row，我会得到两个具有相同值的列，解决方案是根本不选择MyRowNumber。。值是如何进入查询的我不知道，但它是有效的：）我理解第一个，但你在第二个上失去了我：P但是谢谢，我真的需要学习更多的SQL，比我想象的要多得多：）@molde:a
spool
是根据子查询结果构建的临时索引（在您的情况下，它将是
用户名
）上的索引。
即时假脱机
一次为所有值编制索引，而
延迟假脱机
从临时索引返回已编制索引的值，当要求提供尚未编制索引的值时，它将重新扫描子查询并将该值添加到索引中。
(SELECT Count(* ) FROM   user_details)

(SELECT row FROM messageentries WHERE username = 'myUsername')