Question

我是数据库新手，但我遇到了问题：

这里是AAA，BBB，TABLE-1，TABLE-2和TABLE-3表名（表）。

TABLE-1 (A,   B) COMPOUND PRIMARY KEY(A,B) AND A IS REFER FROM *AAA(A)* AND B IS REFER FROM *BBB(B)*
         1    1
         1    2
         2    1

TABLE-2 (D,   A) D IS PRIME AND A IS REFER FROM *AAA(A)*
         1    1
         2    2

TABLE-3 (D,   B) COMPOUND PRIMARY KEY(D,B) AND B IS REFER FROM *BBB(B)*
         1    1
         2    2

HERE MEANING OF TABLE-2 AND TABLE-3 IS 
(D,   A,   B)
 1    1    1
 2    2    2

但问题是第二行A = 2，B = 2与TABLE-1不匹配。

如何实现这一目标？

例如：

    I have Airport, Caterer, Meal, Airport_caterer_map, Airport_Meal_Map
    Airport (this main configuration table)
    id     Name
     1      aaa
     2      bbb
    Caterer   (this main configuration table)
    id     Name
     1      mmm
     2      nnn

    Airport_caterer_map  (this main configuration table)
    airport_id     caterer_id
    1                1
    1                2
    2                1

    Meal
    id     Name  caterer_id
     1      mmm  1
     2      nnn  2

    Airport_Meal_Map
    mail_id    airport_id
    1          1
    1          2
    2          1
    2          2   -- This row should be wrong. 

why is, 
   1. meal 2 is available in airport 2
   2. meal 2 is providing by caterer 2
   3. But there is no mapping between caterer 2 and airport 2 in airport_caterer_map table.

Answer 1

基本上，您的Airport_Meal_Map实际上应该是Airport_Caterer_Meal_Map - 如果您希望数据库帮助进行一致性检查：

CREATE TABLE Airport
  (
   id INT primary key,
   name VARCHAR(30)
  );

INSERT INTO Airport VALUES
(1, 'aaa'),
(2, 'bbb');

CREATE TABLE Caterer
  (
   id INT primary key,
   name VARCHAR(30)
  );

INSERT INTO Caterer VALUES
(1, 'mmm'),
(2, 'nnn');

CREATE TABLE Airport_Caterer_Map
  (
   airport_id INT,
   caterer_id INT,
   PRIMARY KEY (airport_id, caterer_id),
   FOREIGN KEY (airport_id) REFERENCES Airport(id),
   FOREIGN KEY (caterer_id) REFERENCES Caterer(id)
  );

INSERT INTO Airport_Caterer_Map (airport_id, caterer_id) VALUES
(1, 1),
(1, 2),
(2, 1);

-- INSERT INTO Airport_Caterer_Map (airport_id, caterer_id) VALUES
-- (2, 2);

CREATE TABLE Meal
  (
   id INT,
   name VARCHAR(30),
   caterer_id INT,
   PRIMARY KEY (id, caterer_id),
   FOREIGN KEY (caterer_id) REFERENCES Caterer(id)
  );

INSERT INTO Meal (id, name, caterer_id) VALUES
(1, 'mmm', 1),
(2, 'nnn', 2);

-- INSERT INTO Meal (id, name, caterer_id) VALUES
-- (1, 'mmm', 2);

-- INSERT INTO Meal (id, name, caterer_id) VALUES
-- (2, 'nnn', 1);

CREATE TABLE Airport_Meal_Map -- actually Airport_Caterer_Meal_Map
  (
   meal_id INT,
   airport_id INT,
   caterer_id INT,
   PRIMARY KEY (meal_id, airport_id, caterer_id),
   FOREIGN KEY (airport_id, caterer_id) REFERENCES Airport_Caterer_Map(airport_id, caterer_id),
   FOREIGN KEY (meal_id, caterer_id) REFERENCES Meal(id, caterer_id)
  );

INSERT INTO Airport_Meal_Map (meal_id, airport_id, caterer_id) VALUES
(1, 1, 1),
(1, 2, 1),
(2, 1, 2);

-- Fails as meal 1 is not prepared by caterer 2
-- INSERT INTO Airport_Meal_Map (meal_id, airport_id, caterer_id) VALUES
-- (1, 1, 2);

-- Fails as meal 2 is not prepared by caterer 1
-- INSERT INTO Airport_Meal_Map (meal_id, airport_id, caterer_id) VALUES
-- (2, 1, 1);

-- Fails as airport 2 is not served by caterer 2
-- INSERT INTO Airport_Meal_Map (meal_id, airport_id, caterer_id) VALUES
-- (2, 2, 2);

SQL Fiddle

如何在数据库中实现这一目标？

1 个答案: