T-SQL ：避免子查询以支持聚合

Question

我已经使用 T-SQL 很长一段时间了，无法比我更好地进行聚合，这个例子将强调这一点。我敢肯定，可能有一些问题可以解决这个问题，但是，我不知道如何询问它，我也不知道如何更好地搜索它。

我有一个视图可以汇总每个团队成员的一些活动记录 Sample ActivityDetail ...

我需要做的其中一件事是获取给定时间段内所有团队成员的聚合（按成员的活动计数）。我发现使用本网站其他地方的串联黑客可以很容易地在每个成员/活动的专用行中获取每个活动总计

SELECT DISTINCT
      a.Member
    , a.Activity
    , COUNT(CONCAT(a.Member,a.Activity)) AS ActivityCount

FROM v_Activity a 
WHERE    a.Activity_Date > DATEADD(DAY,-7,GETDATE()) 
GROUP BY a.Member,a.Activity
ORDER BY a.Member

Sample ActivityTotals 但是我们在这里真正要寻找的是对此的更统一的表示。现在，我知道我可以像这样为每个 ActivityType 执行 COUNT(*) 子查询来到达那里

SELECT DISTINCT
      a.Member
    , (SELECT COUNT(*) FROM v_UpdateActivity WHERE Member = a.Member AND Activity = 'Create' AND Activity_Date > DATEADD(DAY,-7,GETDATE())) As Created
    , (SELECT COUNT(*) FROM v_UpdateActivity WHERE Member = a.Member AND Activity = 'Update' AND Activity_Date > DATEADD(DAY,-7,GETDATE())) As Updated
    , (SELECT COUNT(*) FROM v_UpdateActivity WHERE Member = a.Member AND Activity = 'Document' AND Activity_Date > DATEADD(DAY,-7,GETDATE())) As Documented
    , (SELECT COUNT(*) FROM v_UpdateActivity WHERE Member = a.Member AND Activity = 'Deactivate' AND Activity_Date > DATEADD(DAY,-7,GETDATE())) As Deactivated
    , (SELECT COUNT(*) FROM v_UpdateActivity WHERE Member = a.Member AND Activity = 'Reactivate' AND Activity_Date > DATEADD(DAY,-7,GETDATE())) As Reactivated

FROM v_cw_ConfigUpdateActivity a 
WHERE    a.Activity_Date > DATEADD(DAY,-7,GETDATE()) 
ORDER BY a.Member

这在获得我想要的输出方面做得不错（包括没有活动的零）。 Desired Output

但是（a）这是低效的 - 它已经表现不佳，并且（b）这只是尖叫聚合，但我显然太厚了，无法想出正确的方法来构建它以获得我正在寻找的东西。有什么帮助吗？

Answer 1

您可以使用 CASE 语句和 GROUP BY 来代替子查询。或者，您可以使用 PIVOT 来执行此操作。

SELECT 
      a.Member
      SUM(CASE WHEM Activity = 'Create' THEN 1 ELSE 0 END) as Created,
      SUM(CASE WHEM Activity = 'Updated' THEN 1 ELSE 0 END) as Updated,
      SUM(CASE WHEM Activity = 'Documented' THEN 1 ELSE 0 END) as Documented,
      SUM(CASE WHEM Activity = 'Deactivated' THEN 1 ELSE 0 END) as Deactivated,
      SUM(CASE WHEM Activity = 'Reactivated' THEN 1 ELSE 0 END) as Reactivated    
FROM v_cw_ConfigUpdateActivity a 
WHERE    a.Activity_Date > DATEADD(DAY,-7,GETDATE()) 
GROUP BY a.Member
ORDER BY a.Member;

我的 tsql 技能可能在这里显示他们的生锈，但这是对 PIVOT 版本的尝试：

SELECT
    Member,
    Created,
    Updated,
    Documented,
    Deactivated,
    Reactivated
FROM (SELECT Member, Activity FROM v_cw_ConfigUpdateActivity) as SourceTable
PIVOT (COUNT(Activity) FOR Member IN (Created, Updated, Documented, Deactivated, Reactivated) as PivotTable