将3个表与单独的where子句连接起来

Question

我有3张桌子：

USERS(id, username, email, password)

QUESTIONS(id, uid, type, ques, date, time)

ANSWERS(id, a_uid, qid, reply, a_date, a_time)

我想从所有三个表中选择*

where $_SESSION[‘id’] = questions.uid

& users.id = questions.uid

& questions.id = answers.qid

我怎样才能实现这一目标？

Answer 1

 select * 
 from USERS
 inner join QUESTIONS  on users.id = questions.userid
 inner join ANSWERS on questions.id = answers.qid
 where  questions.uid = $_SESSION['id'] ;

Answer 2

您可以使用SQL joins来指定where子句。

 select * 
 from USERS U
 join QUESTIONS Q on U.id = Q.uid
 join ANSWERS A on Q.id = A.qid
 where $_SESSION['id'] = Q.uid ;