如何通過做1組並計算SQL子查詢個人組

Question

我有如下表：

date_trans | customerId 
2015-02-01 | 12 
2015-02-01 | 14 
2015-02-01 | 13 
2015-02-01 | 12 
2015-02-02 | 13 
2015-02-02 | 12 
2015-02-02 | 13 
2015-02-02 | 14 
2015-02-02 | 14 

我能夠有一批獲得每日總交易方式：

SELECT date_trans, COUNT(*) as "Transactions" FROM theTable GROUP BY date_trans 

date_trans | Transactions 
2015-02-01 | 4 
2015-02-02 | 5 

但我不能夠通過客戶從同日起部分號碼：

date_trans | Transactions | "By 12" | "By 13" | "By 14" 
2015-02-01 | 4   | 2  | 1  | 1 
2015-02-02 | 5   | 1  | 2  | 2 

我試着做一組由選擇但它不起作用。

我如何在SQL 2014中實現這一點？

謝謝

Answer 1

with trans as (
SELECT date_trans, COUNT(*) as "Transactions" 
FROM theTable 
GROUP BY date_trans) 
, cust as (
SELECT customerid, date_trans, COUNT(*) as "cust_txns" 
FROM theTable 
GROUP BY customerid, date_trans) 
select c.date_trans, 
     t.transactions, 
     case when c.customerid = 12 then cust_txns end as "By 12", 
     case when c.customerid = 13 then cust_txns end as "By 13", 
     case when c.customerid = 14 then cust_txns end as "By 14" 
from trans t join cust c 
on t.date_trans = c.date_trans 

這是做這件事。但是，如果您有許多客戶，則必須使用動態SQL。

編輯：要消除行上的空值，需要更多級別的分組，如下所示。

with trans as (
SELECT date_trans, COUNT(*) as "Transactions" 
FROM thetable 
GROUP BY date_trans) 
, cust as (
SELECT customerid, date_trans, COUNT(*) as "cust_txns" 
FROM thetable 
GROUP BY customerid, date_trans) 
select c.date_trans, 
     max(t.transactions) as transactions, 
     max(case when c.customerid = 12 then cust_txns end) as "By 12", 
     max(case when c.customerid = 13 then cust_txns end) as "By 13", 
     max(case when c.customerid = 14 then cust_txns end) as "By 14" 
from trans t join cust c 
on t.date_trans = c.date_trans 
group by c.date_trans 

SQL Fiddle