Question

Saye 我有一个数据库,有两张表格:“食物”和“小麦”。

I query the "whatToEat" and find 3 rows:

id    Food     username
 1    Apple      John
 2    Banana     John
 3    Milk       Linda

如果我想从“食品”表中获取这些物品,我就能够做这样的想法:

SELECT * 
  FROM food 
 WHERE username= John  AND typeOfFood =  apple  
    OR typeOfFood =  Banana  OR typeOfFood =  Milk

......但还是可以动态地写这句话,因为“ToEat”表将改变所有时间,或者我是否需要一个“食品”表,一个表格是“ToEat”中每个物体的表格?

EDIT

以上只是一个例子,真正的情景是在线游戏。当一个参与者转向游戏时,他就把“事项——更新”摆在桌面上。这份表格只贴上了他的名字,并贴上了配对(或者说,因为他可以同时在几个时间。) 当一个行动者收回最新情况时,我要检查他是否具备需要更新的匹配(频率“配对-更新”表),然后将数据从“配对”表中取回,而所有信息都存放在表上。

例:

The player Tim query the "mathces_updated" table and find he have 2 new matches that needs to be updated:

   match_id   username
    1          Tim
    2          Tim
    2          Lisa
    1           John
    3           John

...... 他现在希望获得有关这些配对的信息,这些信息储存在“配对”表中:

match_id   match_status player1Name Player1Score Player2Name Player2Score
   1           1           John         123         Tim          12
   2           1           Lisa          4          Tim          15
   3           1           John          0          Lisa         0

Answer 1

SELECT * FROM matches_updated JOIN matches
         ON matches_updated.match_id == matches.match_id
         WHERE matches_updated.user == "Tim"

纽约总部

也许你希望有一个

SELECT * FROM food JOIN whattoeat
         ON food.username == whattoeat.username
         WHERE food.username == "John"

I m having a really hard time trying to understand what your desired result is - posting example of both tables in question, and the desired result of your query, might help.

Answer 2

我不清楚我是否正确理解这个问题。

Actually It depends on the queried tables have what in common.

如果食用食品是普通一栏,那么就提出这样的问题。

select * from food where food in (select food from whattoeat where username = ?)

如果它解决了你的问题,它就会提出疑问。

Answer 3

SELECT * FROM food WHERE username= John

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