映射表MySQL/Access

Question

我有一个很短的访问/ mySQL问题。我有以下格式的映射表。

ID  Category_A  Category_B  Category_C  Team 
1    a    b       T1 
2    a        d   T2 

我有第二个表，其中还包括Category_A，Category_B和Category_C。我想根据映射表将我的第二张表加入团队价值。我的问题是，当存在空白时（例如ID = 2，Category_B），映射应将T2分配给包含Category_A = a和Category_C = d的任何行，而不管Category_B中的值如何。

这种类型的映射可以完成吗？

感谢您的帮助！

Answer 1

在MS Access，我想你会需要上线的东西：

SELECT t.ID, m.Team 
FROM Team t 
INNER JOIN Mapping m 
     ON (m.Category_C = t.Category_C) 
    AND (m.Category_B = t.Category_B) 
    AND (m.Category_A = t.Category_A) 
WHERE m.Category_C Is Not Null 
    AND m.Category_B Is Not Null 
    AND m.Category_A Is Not Null 

UNION ALL 
SELECT t.ID, m.Team 
FROM Team t 
INNER JOIN Mapping m 
     ON (m.Category_B = t.Category_B) 
    AND (m.Category_A = t.Category_A) 
WHERE m.Category_C Is Null 
    AND m.Category_B Is Not Null 
    AND m.Category_A Is Not Null 

UNION ALL 
SELECT t.ID, m.Team 
FROM Team t 
INNER JOIN Mapping m 
     ON (m.Category_C = t.Category_C) 
    AND (m.Category_A = t.Category_A) 
WHERE m.Category_C Is Not Null 
    AND m.Category_B Is Null 
    AND m.Category_A Is Not Null 

UNION ALL 
SELECT t.ID, m.Team 
FROM Team t 
INNER JOIN Mapping m 
     ON (m.Category_C = t.Category_C) 
    AND (m.Category_B = t.Category_B) 
WHERE m.Category_C Is Not Null 
    AND m.Category_B Is Not Null 
    AND m.Category_A Is Null