在分组TSQL查询

Question

总计数我有一个性能有很高的查询，过滤掉根据其它表等

数据很多不需要的记录，我平均一列，也返回计数各均线组。这一切工作正常。

但是，我还想包括TOTAL计数的百分比。

有没有什么方法可以在不重新运行整个查询的情况下获得总计数，或者显着提高性能负载？

如果我不需要完全重构子查询（例如通过获取总数以外），我还会更喜欢，但如果需要可以做。

SELECT 
    data.EquipmentId, 
    AVG(MeasureValue) AS AverageValue, 
    COUNT(data.*) AS BinCount 
    COUNT(data.*)/ ???TotalCount??? AS BinCountPercentage 
FROM 
(SELECT * FROM MultipleTablesWithJoins) data 
GROUP BY data.EquipmentId 

Answer 1

参见Window functions。

SELECT 
    data.EquipmentId, 
    AVG(MeasureValue) AS AverageValue, 
    COUNT(*) AS BinCount, 
    COUNT(*)/ cast (cnt as float) AS BinCountPercentage 
FROM 
(SELECT *, 
     -- Here is total count of records 
     count(*) over() cnt 
FROM MultipleTablesWithJoins) data 
GROUP BY data.EquipmentId, cnt 

编辑：忘记做除法的数字。

Answer 2

另一种方法：

with data as 
(
    SELECT * FROM MultipleTablesWithJoins 
) 
,grand as 
(
    select count(*) as cnt from data 
) 
SELECT 
    data.EquipmentId, 
    AVG(MeasureValue) AS AverageValue, 
    COUNT(data.*) AS BinCount 
    COUNT(data.*)/ grand.cnt AS BinCountPercentage 
FROM data cross join grand 
GROUP BY data.EquipmentId