SQL Server：2个Pivot问题

Question

我到目前为止看到的所有数据透视示例都使用聚合函数。所以我不知道如何实现以下目标：

我有这个简单的表用于测试目的：

;WITH cte AS (
SELECT * FROM (VALUES
(1, 'Messi',    'Graz'),
(2, 'Ronaldo',  'Graz'),
(3, 'Weah',     'Wien'),
(4, 'Nedved',   'Wien'),
(5, 'Hagi',     'Wien'),
(6, 'Puskas',   'Istanbul'),
(7, 'Stoichkov', 'Dubai'),
(8, 'Di Baggio', 'Dubai')
) as t(cid, name, city))

我想实现以下目标：

1. 要像这样旋转表格：

   

2. 我想轮换以下查询：

   SELECT city, COUNT(city) AS num_of_customers 
   FROM CUSTOMERS 
   GROUP BY city;
   

产生以下结果：



我想这样显示：



到目前为止，我从未使用数据透视表，我将不胜感激任何帮助。

PS：表格名称为Customers。

Answer 1

这两个查询都很容易以动态方式进行，如果你没有固定数量的行并且需要查询来适应行数，这很好。

第一个查询：

DECLARE @players AS VARCHAR(MAX)
SELECT @players = STUFF((SELECT DISTINCT ',['+CAST(cid AS VARCHAR(10))+']'
FROM customers FOR XML PATH('')),1,1,'')
DECLARE @dynamic_pivot_query AS VARCHAR(MAX)

SET @dynamic_pivot_query = 'SELECT '+@players+'
  FROM (SELECT cid, name FROM customers) AS S
  PIVOT (MAX(name) FOR cid IN ('+@players+')
) AS P'

EXEC(@dynamic_pivot_query)

结果：

1       2       3       4       5       6       7           8
Messi   Ronaldo Weah    Nedved  Hagi    Puskas  Stoichkov   Di Baggio

第二个问题：

DECLARE @cities AS VARCHAR(MAX)
SELECT @cities = STUFF((SELECT DISTINCT ',['+city+']'
FROM customers FOR XML PATH('')),1,1,'')

DECLARE @dynamic_pivot_query AS VARCHAR(MAX)
SET @dynamic_pivot_query = 'SELECT '+@cities+' 
   FROM (SELECT city FROM customers) as S
   PIVOT (COUNT(city) FOR city IN ('+@cities+')
) AS P'

EXEC(@dynamic_pivot_query)

结果：

Dubai       Graz        Istanbul    Wien
----------- ----------- ----------- -----------
2           2           1           3

Answer 2

可以实现第二次查询，如下所示

select Dubai,Graz,Istanbul,Wien
from Customers
pivot
(
COUNT(city)
for city
in ([Dubai],[Graz],[Istanbul],[Wien])
)
as pivottab