Question

我有餐桌食品，有以下限制

Food

Name(which has the dish name)
category (cuisine name)
DeskNo(The table that it is placed on)


Food:
Name         Category     Deskno
pasta        Mexican         1
noodles      Chines          1
friedrice    Chinese         2
Tamarindrice Indian          2

我有一张带有

的通过表格

ThroughAway

category1
category2

ThrowAway
Category1      Category2
Indian         Chinese
Mexican        Indian

如果category1和category2聚集在同一桌面上，那些菜肴将被扔掉。我需要输出同一DeskNo中菜肴的名称，并且存在两者都可能落入ThrownAway的危险。需要一些帮助

Answer 1

尝试此查询

SELECT Distinct a.Name AS Dish1, b.Name As Dish2
FROM Food a, Food b, ThroughAway c
WHERE a.Name <> b.Name AND a.Deskno = b.deskno AND 
(a.category = c.category1 AND c.category2 = b.category) ;

自我加入，将同桌的菜肴与扔掉的桌子进行比较

小提琴 http://sqlfiddle.com/#!2/0893e6/7

Answer 2

select f1.name, f2.name from ThrowAway t
inner join Food f1 on f1.Category = t.Category1
inner join Food f2 on f2.Category = t.Category2
where f1.deskno = f2.deskno

但你不应该像这样加入varchar或者smth，这是一个非常糟糕的做法。添加ID，索引并加入它们。

Answer 3

SELECT FOOD.DESKNO
FROM   FOOD INNER JOIN
THROW ON FOOD.CATEGORY = THROW.CAT1 INNER JOIN
THROW AS THROW_1 ON FOOD.CATEGORY = THROW_1.CAT2

Answer 4

食品

姓名（有菜名）类别（美食名称） DeskNo（放置它的表）

食物：名称分类Deskno 面食墨西哥1 面条中国1 Friedrice中文2 Tamarindrice Indian 2

食物选择查询

4 个答案: