我有有用户,问题,并答案的SQL。我想要一个包含问题比率的联结表。许多用户可以评价很多问题。你能告诉我这个SQL有什么问题吗?这里是SQL:多对多SQL
CREATE TABLE user
(
user_id int(4) NOT NULL,
user_name varchar(255) NOT NULL,
PRIMARY KEY (user_id)
);
CREATE TABLE question
(
question_id int(4) NOT NULL,
question_text longtext NOT NULL,
user_id int(4) NOT NULL,
PRIMARY KEY (question_id),
FOREIGN KEY (user_id) REFERENCES user(user_id)
);
CREATE TABLE answer
(
answer_id int(4) NOT NULL,
user_id int(4)NOT NULL,
question_id int(4) NOT NULL,
PRIMARY KEY (answer_id),
FOREIGN KEY (user_id) REFERENCES user (user_id),
FOREIGN KEY (question_id) REFERENCES question (question_id)
);
CREATE TABLE rate
(
user_id int(4) REFERENCES user NOT NULL,
question_id int(4) REFERENCES question NOT NULL,
rate int(4) NOT NULL
)
为我们提供了一个指导,告诉您如何让它们相关,因为我认为您的概念错了。即用户不应该与IMO问题相关联。 – ericosg 2013-04-29 15:18:37