按天分組然後統計每天的結果

Question

我很難解決這個問題。我使用的是MS SQL 2008，我有一個名爲Activity的表格，其中包含3個字段：客戶（客戶的身份），visitDate（他們訪問的日期）和customerType（他們是什麼類型的客戶）。以下是通過3天的數據：

customer visitDate     customerType 

customer1 2013-10-01 07:00:00.000  A 
customer1 2013-10-01 09:00:00.000  A 
customer2 2013-10-01 10:00:00.000  B 

customer1 2013-10-02 09:00:00.000  A 
customer2 2013-10-02 09:00:00.000  B 
customer3 2013-10-02 09:00:00.000  B 
customer1 2013-10-02 09:00:00.000  A 

customer1 2013-10-03 07:00:00.000  A 

我試圖做到的，是寫一個查詢，數據組顯示的每一天也計算在用戶鍵入的每一天，這樣的結果是這樣的：

visitDate TypeA TypeB Total 

2013-10-01 1  1  2 
2013-10-02 1  2  3 
2013-10-03 1  0  0 

請注意，如果某人在同一天訪問超過一次，那麼他們僅計爲當天的一次訪問。

我知道這與分組有關，但我還沒有弄清楚從哪裏開始。

Answer 1

略微有點棘手是隻在指定的日子和類型算一個客戶一次，即使他們有多個記錄這一天的到來：

select 
    visitDate, 
    sum(case when customerType = 'A' then 1 else 0 end) as TypeA, 
    sum(case when customerType = 'B' then 1 else 0 end) as TypeB, 
    count(*) as Total 
from (
    select distinct 
     customer, 
     cast(visitdate as date) as visitdate, 
     customertype from activity 
    ) x 
group by 
    visitdate 

Example SQLFiddle

Answer 2

select visitDate, 
     sum(case when customerType = 'A' then 1 else 0 end) as TypeA, 
     sum(case when customerType = 'B' then 1 else 0 end) as TypeB, 
     count(*) as Total 
from activity 
group by visitDate 

Answer 3

這也將削減DateTime場的部分時間：

select 
    cast(visitDate as Date) as visitDate, 
    sum(case customerType when 'A' then 1 else 0 end) as TypeA, 
    sum(case customerType when 'B' then 1 else 0 end) as TypeB, 
    count(*) as Total 
from activity 
group by cast(visitDate as Date)