从group和cte到变量添加count（*）？

Question

表@sales的内容基本上是每个城市最畅销的汽车品牌。这是说丰田在 Houston 和 Chicago 等中销售最多。

此查询的结果（我知道可能更好）显示了哪些品牌被绑定以及绑定的次数。例如， Chevy 并列两个城市的第一名， Ford 并列在一个城市（迈阿密），依此类推。

如何根据count(*)将CarSoldMost添加到变量中？在这种情况下，我会将2添加到@chevy，将1添加到@ford等等吗？

我正在考虑使用case语句，但它的使用不正确。

declare @toyota int = 0
declare @nissan int = 0
declare @chevy int = 0
declare @ford int = 0

declare @sales table
(
    city varchar(10),
    CarSoldMost varchar(10)
)
insert into @Sales
select 'Chicago', 'Toyota' union
select 'Orlando', 'Nissan' union
select 'miami', 'Ford' union
select 'miami', 'Chevy' union
select 'houston', 'Toyota' union
select 'houston', 'Chevy'

select *From @sales


;with cte as 
(
    select city
    from @sales
    group by city
    having count(*) > 1
) --select carsoldmost, count(*) from @sales where city in (select city from cte) 
group by carsoldmost
select @chevy = 
case 
    when carsoldmost = 'chevy' then @chevy+count(*)
    when carsoldmost = 'Ford' then @ford+count(*)
  end
from @sales where city in (select city from cte) group by carsoldmost

select @chevy, @ford

Answer 1

变量的分配需要使用单独的case 表达式完成：

-- Sample data.
declare @Sales as Table(
  City VarChar(10),
  CarSoldMost VarChar(10) );
insert into @Sales ( City, CarSoldMost ) values
  ( 'Chicago', 'Toyota' ),
  ( 'Orlando', 'Nissan' ),
  ( 'Miami', 'Ford' ),
  ( 'Miami', 'Chevy' ),
  ( 'Houston', 'Toyota' ),
  ( 'Houston', 'Chevy' );
select * from @Sales;

-- Summary variables.
declare @Chevy int = 0, @Ford int = 0, @Nissan int = 0, @Toyota int = 0;

-- Summary query.
with cte as (
  select City
    from @Sales
    group by City
    having Count(*) > 1 )
  select
    @Chevy += case when CarSoldMost = 'Chevy' then Count(*) else 0 end,
    @Ford += case when CarSoldMost = 'Ford' then Count(*) else 0 end,
    @Nissan += case when CarSoldMost = 'Nissan' then Count(*) else 0 end,
    @Toyota += case when CarSoldMost = 'Toyota' then Count(*) else 0 end
    from @Sales
    where City in ( select City from cte )
    group by CarSoldMost;

-- Display the results.
select @Chevy as 'Chevy', @ford as 'Ford', @Nissan as 'Nissan', @Toyota as 'Toyota';

Answer 2

使用条件聚合已经发布的其他变体

-- display result/or replace aliasis by variables to assign values.
select 
  Chevy = Count(case when CarSoldMost = 'Chevy' then 1 end) ,
  Ford = Count(case when CarSoldMost = 'Ford' then 1 end),
  Nissan = Count(case when CarSoldMost = 'Nissan' then 1 end),
  Toyota = Count(case when CarSoldMost = 'Toyota' then 1 end)
from @Sales as a
Where City in (select City 
               from @Sales
               group by City
               having count(City)>1)

测试：