为没有任何对应值的组生成记录

Question

请考虑以下脚本：

declare @Table_City     table(CityName   varchar(50));
declare @Table_Product      table(ProductName   varchar(50));
declare @Table_Data     table(CityName   varchar(50), ProductName  varchar(50), [Count]    int, Price    int)

insert into @Table_City values('Paris'),('London'),('Tokyo'),('Roma'),('Bern'),('Aten')
insert into @Table_Product values('Toys'),('Shoe'),('TV'),('Radio')
insert into @Table_Data values
    ('Paris', 'Shoe', 12, 10000),
    ('Paris', 'TV', 6, 1040),
    ('Bern', 'Radio', 1, 10),
    ('London', 'TV', 32, 21132),
    ('Roma', 'Shoe', 120, 654400),
    ('Aten', 'TV', 20, 35000),
    ('Paris', 'Radio', 17, 2000),
    ('Paris', 'Radio', 2, 300),
    ('Tokyo', 'TV', 100, 1002000),
    ('Aten', 'TV',20 ,4000 ),
    ('Bern', 'TV', 35, 5000),
    ('London', 'Radio', 70, 7000),
    ('London', 'TV',10 ,10000 ),
    ('Aten', 'Shoe',200 ,10500 ),
    ('London', 'Toys', 10, 8000),
    ('Paris', 'Toys',80 , 9000),
    ('Paris', 'Radio',50 ,75000 ),
    ('Tokyo', 'Shoe',45 ,5500 ),
    ('Roma', 'Toys',12 ,6000 ),
    ('Bern', 'Toys',50 ,4800 ),
    ('London', 'TV',40 ,8700 ),
    ('Aten', 'Toys', 80 ,2500 ),
    ('Aten', 'TV', 100 ,12500 )

select CityName, ProductName , sum([count]) , sum(price)
from @Table_Data
group by CityName, ProductName
order by 1, 2

此脚本生成以下结果：

但是我想要这个结果：

为那些没有相应组值的记录生成0条记录的最佳方法是什么？

Answer 1

先使用Navigator.push(context, MaterialPageRoute(builder: (context) => Page2())).then((value) { setState(() { // refresh state }); }); ，isnull()，然后再加入我们的cross apply

tabledata

Answer 2

您用CROSS JOIN @Table_City @Table_Product，然后LEFT JOIN到@Table_Data

SELECT c.CityName, p.ProductName, 
       SUM(COALESCE([Count], 0)) as [Count],
       SUM(COALESCE([Price], 0)) as [Price]
FROM   @Table_City c
       CROSS JOIN @Table_Product p
       LEFT  JOIN @Table_Data d     ON c.CityName    = d.CityName
                                   AND p.ProductName = d.ProductName
GROUP BY c.CityName, p.ProductName