连接的mysql查询结果问题

Question

I have multiple tables as table_1 has id , p_code, profile_status, name and table_2 has id, p_code, availablity and table_3 has id, p_code, status... How to get all records form all tables depend on p_code. table_2 and table_3 has few records. if p_code not in table_2 and table_3 then echo 'no' in results. currently i am using my query as below

select t.id, t.p_code,t.name,t.num_rooms, t.profile_status, t.distance FROM (  
     (        SELECT id , p_code, profile_status, name,num_rooms, 3956 * 2 *  ASIN(SQRT( POWER(SIN(($origLatAirport - latitude)*pi()/180/2),2)
      +COS($origLatAirport*pi()/180 )*COS(latitude*pi()/180)
      *POWER(SIN(($origLonAirport-longitude)*pi()/180/2),2))) 
      as distance FROM property WHERE   profile_status=1 having distance < ".$dist." )  ) as t 

How to add table_2 and table_3 and fetch results. Pleasr reply soon. I am stuck here.

Answer 1

In your query you are doing CROSS JOIN and what you desire, is probably INNER JOIN .

In MySQL the CROSS JOIN behaves like JOIN and INNER JOIN of without using any condition. The CROSS JOIN returns all rows form user multiplied by all rows from user_inbox - for every user you get inboxes of all users.

You should specify condition for your JOIN statement.

 $sql_alt = mysql_query(
    "select i.*,u.images, u.firstname, u.lastname 
         from user_inbox i INNER JOIN user u ON i.to_id = u.user_id
         where i.to_id = '$user_id'");

Also it is good habit have the same names for primary and foreign keys, so I think you should have user_id or user_id_to instead of to_id in your user_inbox table. This is of course not absolutely necessary.