Question

CREATE TABLE members
(
name        varchar(40),
ID          char(6)         PRIMARY KEY
);

CREATE TABLE games
(
name        varchar(100),
ID      serial                  PRIMARY KEY
);

CREATE TABLE ratings
(
memberID    char(6)            REFERENCES members(ID),
rating      SMALLINT CHECK(rating >= 1 AND rating <= 8),
gameID      integer            REFERENCES games(ID),
        PRIMARY KEY (memberID, gameID)
);

我正在尝试查找每位评分为ID的（2）跟随游戏的所有评分。

我用过：

SELECT rating, name 
    FROM ratings, members 
    WHERE gameID = 2;

每当我使用此命令时，它会给我正确的评级值，但它会列出所有成员，即使该成员没有评价游戏。有人可以帮助弄清楚如何解决问题。

提前感谢所有

Answer 1

您正在寻找JOIN：

SELECT rating, name 
FROM ratings r
     INNER JOIN members m
       ON r.MemberID = m.ID
WHERE gameID = 2;

Answer 2

尝试：

SELECT rating, name 
FROM ratings, members 
WHERE gameID = 2 and ratings.memberID = members.id;

查找在SQL中对其进行评级的每个成员给予某个游戏的评级

2 个答案: