使用窗口函数获取总数

Posted 2023-03-31

【中文标题】使用窗口函数获取总数

【英文标题】：Get total count using a window function

【发布时间】：2016-09-16 19:54:37

【问题描述】：

嘿，这就是我目前的查询：

WITH LIMIT AS
        (SELECT 
             U.userID
            ,U.username
            ,U.fname    
            ,U.mname    
            ,U.lname    
            ,U.email    
            ,U.active 
            ,S.sName
            ,S.sID
            ,T.[value]
            ,T.trackingNumberID
            ,SU.primaryLocation
            ,row_number() OVER (ORDER BY U.userid) AS RN 
            ,COUNT(*) OVER (ORDER BY U.userid) AS CNT 
            ,UR.roleID
        FROM 
            [---].[dbo].[tblUsers]                          AS U
        LEFT OUTER JOIN [---].[dbo].[tblTrackingNumbers]    AS T
            ON T.userID = U.userID
        LEFT OUTER JOIN [---].[dbo].[tblSU]                 AS SU
            ON U.userID = SU.userID
        LEFT OUTER JOIN [---].[dbo].[tblS]                  AS S
            ON SU.sID = S.sID 
        LEFT OUTER JOIN [---].[dbo].[tblUserRoles]          AS UR 
            ON UR.userID = U.userID
        LEFT OUTER JOIN [---].[dbo].[tblRoles]              AS R 
            ON UR.roleID = R.roleID
        WHERE 
            U.active = 1 
        AND 
            SU.primaryLocation = 1
        AND 
            SU.active = 1 
        AND 
                U.orgID = 1
            AND 
                S.ID = 35 
            AND U.userID IN (SELECT userID 
                              FROM [---].[dbo].[tblSU] AS SU 
                              INNER JOIN [].[dbo].[tblS] AS S 
                                 ON S.sID = SU.sID 
                              WHERE 
                                 SU.active = 1 
                              AND 
                                 S.sID = 35)
) SELECT * FROM LIMIT WHERE RN Between 0 AND 10000

正如您在上面的查询中看到的那样，我正在尝试 COUNT(*) OVER (ORDER BY U.userid) AS CNT 这给了我与 RN 相同的计数.

我需要的是记录总数这将带回（842行）。

【问题讨论】：

只做 Count(*) 并且不要对其进行分区。这不应该是你需要的吗？

哈就是@a_horse_with_no_name。请将其作为官方答案，以便我给予您信任。

您是否使用 RN 只是为了限制少于 1000 行？请先使用 Top 或 Fetch... 更快。

【参考方案1】：

COUNT(*) OVER (ORDER BY U.userid) AS CNT 计算“运行计数” - 直到“那个”行的计数。如果要计算完整结果中的所有行，请使用不带order by 的窗口函数

COUNT(*) OVER () AS CNT

【参考方案2】：

这可能听起来很奇怪，但我发现对于大型表，如果您将计数选择到变量中，然后选择记录并添加变量，您可以获得更好的性能。当表变得太大时，带有 count(*) over() 的东西会导致性能下降。

DECLARE @RecordCount INT
SELECT  @RecordCount = COUNT(*)
FROM    [---].[dbo].[tblUsers] AS U
        LEFT OUTER JOIN [---].[dbo].[tblTrackingNumbers] AS T ON T.userID = U.userID
        LEFT OUTER JOIN [---].[dbo].[tblSU] AS SU ON U.userID = SU.userID
        LEFT OUTER JOIN [---].[dbo].[tblS] AS S ON SU.sID = S.sID
        LEFT OUTER JOIN [---].[dbo].[tblUserRoles] AS UR ON UR.userID = U.userID
        LEFT OUTER JOIN [---].[dbo].[tblRoles] AS R ON UR.roleID = R.roleID
WHERE   U.active = 1
        AND SU.primaryLocation = 1
        AND SU.active = 1
        AND U.orgID = 1
        AND S.ID = 35
        AND U.userID IN (SELECT userID
                         FROM   [---].[dbo].[tblSU] AS SU
                                INNER JOIN [].[dbo].[tblS] AS S ON S.sID = SU.sID
                         WHERE  SU.active = 1
                                AND S.sID = 35)

SELECT  U.userID,
        U.username,
        U.fname,
        U.mname,
        U.lname,
        U.email,
        U.active,
        S.sName,
        S.sID,
        T.[value],
        T.trackingNumberID,
        SU.primaryLocation,
        @RecordCount AS CNT,
        UR.roleID
FROM    [---].[dbo].[tblUsers] AS U
        LEFT OUTER JOIN [---].[dbo].[tblTrackingNumbers] AS T ON T.userID = U.userID
        LEFT OUTER JOIN [---].[dbo].[tblSU] AS SU ON U.userID = SU.userID
        LEFT OUTER JOIN [---].[dbo].[tblS] AS S ON SU.sID = S.sID
        LEFT OUTER JOIN [---].[dbo].[tblUserRoles] AS UR ON UR.userID = U.userID
        LEFT OUTER JOIN [---].[dbo].[tblRoles] AS R ON UR.roleID = R.roleID
WHERE   U.active = 1
        AND SU.primaryLocation = 1
        AND SU.active = 1
        AND U.orgID = 1
        AND S.ID = 35
        AND U.userID IN (SELECT userID
                         FROM   [---].[dbo].[tblSU] AS SU
                                INNER JOIN [].[dbo].[tblS] AS S ON S.sID = SU.sID
                         WHERE  SU.active = 1
                                AND S.sID = 35)
ORDER BY U.userID
OFFSET 0 ROWS FETCH NEXT 10000 ROWS ONLY