Convert complex JOIN query in codeigniter - php

Question

I'm converting my existing website to CI, and I have been trying for several days to convert this query to CI-friendly code:
$result = mysql_query("
SELECT t1.mnumber, t1.mcontent, t1.mcontact
FROM sms t1
JOIN (
SELECT mContent,mcontact, mnumber, MAX(mID) mID
FROM sms
GROUP BY mContact
) t2 ON t1.mcontact = t2.mcontact AND t1.mid = t2.mid
GROUP BY t1.mContact
ORDER BY t1.mid DESC
");
But no matter what I try, I can't get the correct result on CI.
I hope you guys can help me out here!
The closest to a result that i did get, was when i used the subquery hack.
However, out of frustration i deleted the block of code and kept trying.
I decided to use a flat query, like the one posted above. This almost gives me results.
$query = $this->db->query("SELECT t1.mnumber, t1.mcontent, t1.mcontact FROM sms t1
JOIN (SELECT mContent,mcontact, mnumber, MAX(mID) mID FROM sms GROUP BY mContact) t2
ON t1.mcontact = t2.mcontact AND t1.mid = t2.mid GROUP BY t1.mContact ORDER BY t1.mid DESC");
$contacts = array();
//Add data to our array
foreach($query->result() as $row){
echo $row->mNumber;
}
return $contacts;
However, in my view i get the notice "Message: Undefined property: stdClass::$mNumber"
So still no results, plus i prefer the CI query method.

Answer 1

You can use it in codeigniter like this
$query = " SELECT t1.mnumber, t1.mcontent, t1.mcontact
FROM sms t1
JOIN (
SELECT mContent,mcontact, mnumber, MAX(mID) mID
FROM sms
GROUP BY mContact
) t2 ON t1.mcontact = t2.mcontact AND t1.mid = t2.mid
GROUP BY t1.mContact
ORDER BY t1.mid DESC";
$result = $this->db->query($query);
return $result->result();
2nd Method
You can use sub query way of codeigniter to do this for this purpose you
will have to hack codeigniter. like this. Go to system/database/DB_active_rec.php
Remove public or protected keyword from these functions
public function _compile_select($select_override = FALSE)
public function _reset_select()
Now subquery writing in available And now here is your query with active record
$select = array(
'mContent',
'mcontact',
'mnumber',
'MAX(mID) mID'
);
$this->db->select($select);
$this->db->from('sms');
$this->db->group_by('mContact');
$subquery = $this->db->_compile_select(); // get the query string
$this->db->_reset_select(); // reset so it can newly form the query
unset($select);
$select = array(
't1.mnumber',
't1.mcontent',
't1.mcontact'
);
$this->db->select($select);
$this->db->join('',"($subquery)");
$this->db->from('sms t1');
$this->db->group_by('t1.mContact');
$this->db->order_by('t1.mid','DESC');
$result = $this->db->get();
return $result->result();
And the thing is done. Cheers!!!
Note : While using sub queries you must use
$this->db->from('myTable')
instead of
$this->db->get('myTable')
which runs the query.

Answer 2

Er, shouldn't that be (at a guess)...
SELECT t1.mnumber
, t1.mcontent
, t1.mcontact
, t1.mid
FROM sms t1
JOIN
( SELECT mcontact
, MAX(mID) mID
FROM sms
GROUP BY mContact
) t2
ON t1.mcontact = t2.mcontact
AND t1.mid = t2.mid
ORDER
BY t1.mid DESC;

Answer 3

This may not fully answer your question, but for those of you who are Googling for a "JOIN AND" (so that you can AND some extra stuff on the Join, before the WHERE clause kicks in), here's a hacky way to do it:
$this->db->join('table_to_join', 'first_table.connect_id = table_to_join.id AND table_to_join.some_filter != 0');
Definitely not pretty, but that obviously forces the AND to occur immediately after the JOIN, before you get into the WHERE stuff for the rest of your query on first_table

Answer 4

Well, its easy to implement in CI version 3+
$subQuery = $this->db->select( 'table2.*' )
->join( 'table3', 'table3.orderId = table2.fkOrderId', 'INNER' )
->where()->get_compiled_select( 'table2' );
$this->db->select( 'table1.*' )
->join( '(' . $subQuery . ') AS b', 'b.`fkCouponId` = table1.couponId', 'LEFT', FALSE )
->get( 'table1' )
TIP: Make sure you don't use any query builder methods above the subquery part.