php - 通过连接从 2 个以上 mysql 表中获取数据。

Question

这是我的表结构。

Table1  // it has 4 colums,that saves all the question posted by user

id|question|answer|postby|

Table2  //it has 2 colums, that saves all the signed up users

id|username|email|

Table3 //it saves that which question is read by which user.

id|reader_id|question_id| 

注意:reader_id是表2的id。

问题:我们需要找出特定用户没有阅读的问题。

Answer 1

select * from table1 where id not in (
    select question_id from table3 where reader_id = [particular user id]
)