MySQL 3 tables single query for Datatables

Question

I'm trying to get data from 3 tables in one query. Those tables are for storing and displaying user messages. Each user can log in and request all his inbox messages. The user id is avaliable from the PHP session and parameter type=1 gets passed in the php request which means the request to show inbox (type=2 would be info messages etc).

First table called email has id, subject, body and date

Second table called email_routing has message_id, sender_email_id, receiver_email_id, basket, type. The message_id refers to id of the message in email table.

Sender and receiver id refers to email ids from the third table that called people_emails. It consist of id(that what sender and receiver email id refer to), internal_user_id (that's what is avaliable from PHP session), email and people_id (each person may have several emails in the contact book so I store people and their emails in separate tables, but this last column if not of our interest here).

So I can figure out how I would do my queries in sequence and just for one row result:

Fist I would get user email id based on his user_id from PHP session:

$X = SELECT `id` from `people_emails` WHERE `internal_user_id`=$_conf[user]->id;

$X is not a proper coding, let's say it is a variable I would eventually get.

Then I can query the email_routing table to all the messages addressed to that user:

$Y = SELECT `message_id`, `sender_email_id`, `receiver_email_id` FROM `email_routing` WHERE `receiver_email_id`=$X[id] and `type`=$_REQUEST[type];

Having list of the message_id's I can now query the email table for the messages content:

$R = SELECT `subject`, `body`, `date` FROM `email` WHERE `id`=$Y[message_id];

Ok, then I need to "translate" the "from" addresses from its id which I got from email_routing table, so it is:

$Z_from = SELECT `email` FROM `people_emails` WHERE `id`=$X[sender_email_id];

I now have all the data for one row. Then I need to put all together which will be

$Z_from + $R[subject] + $R[body] + $R[date]

I need to have it as one list of results which then gets passed to bootstrap datatables plugin for displaying and searching. I can't seem to figure that one out. Please help.

What you are looking for is called a `join` – Daryl Gill Aug 28 '13 at 21:39 — Daryl Gill, Aug 28 '13 at 21:39

spencer7593 · Accepted Answer · 2013-08-29T17:32:08.927

Your queries, reformatted:

$X:  SELECT p.id
       FROM people_emails p 
      WHERE p.internal_user_id = $_conf[user]->id;

$Y:  SELECT r.message_id
          , r.sender_email_id
          , r.receiver_email_id
       FROM email_routing r 
      WHERE r.receiver_email_id = $X[id] 
        AND r.type = $_REQUEST[type];

$R:  SELECT e.subject
          , e.body
          , e.date
       FROM email e
      WHERE e.id = $Y[message_id];

$F:  SELECT s.email
       FROM people_emails s 
      WHERE s.id = $Y[sender_email_id]

To return these columns:

$F + $R[subject] + $R[body] + $R[date]

The queries can be combined like this:

 SELECT s.email AS sender_email
      , e.subject
      , e.body
      , e.date
   FROM people_emails p 
   JOIN email_routing r 
     ON r.receiver_email_id = p.id
    AND r.type = $_REQUEST[type]
   JOIN email e
     ON e.id = r.message_id
   JOIN people_emails s
 ON s.id = r.sender_email_id
  WHERE p.internal_user_id = $_conf[user]->id;

FOLLOWUP

To add the sender full_name from the people table, we can add a join to that table, and add the column to the SELECT list:

$N = SELECT n.full_name
       FROM people n 
      WHERE n.id = (SELECT s.people_id
                      FROM people_emails s 
                     WHERE s.email = :sender_email
                   )

We already have :sender_email from the query above, it's the value returned from s.email in the SELECT list, so we can just add a join to the people table:

 SELECT s.email     AS sender_email
      , n.full_name AS sender_full_name
      , e.subject
      , e.body
      , e.date
   FROM people_emails p 
   JOIN email_routing r
     ON r.receiver_email_id = p.id
    AND r.type = $_REQUEST[type]
   JOIN email e
     ON e.id = r.message_id
   JOIN people_emails s
 ON s.id = r.sender_email_id
   JOIN people n
     ON n.id = s.people_id
  WHERE p.internal_user_id = $_conf[user]->id;

(I can't really test this, since I don't have your table definitions or sample data.)

That's brilliant! Thank you, that worked exactly as I needed. I had a bit hard time to pass it to datatables then but I found a way to do this. At the end I suddently realized that I need one more column which is `full_name` of sender stored in **people** table and can be found by SELECT `full_name` FROM people WHERE id=(SELECT people_id FROM `people_emails` WHEERE `email`=sender_email); I have tried to add f.full_name right after SLECT in your example and then add "JOIN people f ON f.id = s.people_id" but I get full_name of myown (receiver name), no the sender_name. — user164863, Aug 29 '13 at 17:06
Great! That's worked immediatly right. Thank you. I guess I have to learn this JOIN as I don't know how you do it but it gets the needed result. — user164863, Aug 30 '13 at 20:41

MySQL 3 tables single query for Datatables

1 Answers1

FOLLOWUP