Sql 将表1中具有键值的两个表与表2中的所有键值连接起来

我有两张桌子

表1:带有列名

键

价值观：

表2:有三列

产品

，

类别

，

计数

P1-C1-2  
P1-C3-4  
P2-C1-3  
P2-C2-4,  
P2-C3-8,   
P3-C3-10,  
P3-C4-2,  

所需输出：

P1-C1-2  
P1-C2-0  
P1-C3-0  
P1-C4-0  
P2-C1-3  
P2-C2-4,  
P2-C3-8,  
P2-C4-0,  
P3-C1-0,  
P3-C2-0,  
P3-C3-10,  
P3-C4-2

有什么办法吗

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提前感谢

看起来您想使用交叉连接：

SELECT [* | column_list]
FROM table1
CROSS JOIN table2;

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您正在寻找

交叉连接

select distinct t2.Product, t1.Key, coalesce(t3.count, 0) as count 
from table2 t2 cross join (select [Key] from table1) t1
left join table2 t3 
          on t3.Product = t2.Product and t1.[key] = t3.Category

select distinct t2.Product, t1.Key, coalesce(t3.count, 0) as count 
from table2 t2 cross join (select [Key] from table1) t1
left join table2 t3 
          on t3.Product = t2.Product and t1.[key] = t3.Category

SELECT t2.Product,t2.Category, case when t2.Category=t1.Category then t2.count ELSE 0 END AS count
FROM table1 t1,table2 t2;