Multiple Joins in Codeigniter

Question

I\'m new to building databases and I\'m trying to do a JOIN based on a having three database tables.

Table A = ID, Name, etc
Table B = ID, Name, etc
Table C          


        

Answer 1

$this->db->select('*');
$this->db->from('TableA AS A');// I use aliasing make joins easier
$this->db->join('TableC AS C', 'A.ID = C.TableAId', 'INNER');
$this->db->join('TableB AS B', 'B.ID = C.TableBId', 'INNER');
$result = $this->db->get();

The join function works like this: join('TableName', 'ON condition', 'Type of join');

The equivilent sql:

SELECT *
FROM TableA AS A
    INNER JOIN TableC AS C
    ON C.TableAId = A.ID
    INNER JOIN TableB AS B
    ON B.ID = C.ID

I found that writing the SQL first, testing it, then converting to the active record style minimizes error.

Answer 2

if you want a flexible query you could use:

http://codeigniter.com/user_guide/database/results.html

which utilizes the following syntax $query = $this->db->query('SELECT * FROM my_table');

here is the query:

SELECT a.name as namea ,b.name as nameb FROM tablec c
JOIN tablea a ON a.ID = c.ID
JOIN tableb b ON b.ID = c.ID

you may want to read more about joins here

then go through your results in such a way:

$query = $this->db->query("YOUR QUERY");

foreach ($query->result_array() as $row)
{
   echo $row['namea'];
   echo $row['nameb'];
}

Answer 3

$this->db->select('*');

$this->db->from('table1');

$this->db->join('table2','table1.id=table2.id'); 

$this->db->join('table3','table2.id=table3.id');

$this->db->join('table4','table3.id=table4.id'); 

$this->db->join('table5','table5.id=table4.id');

$this->db->where('table5.id',$this->session->userdata('id'));//getting value from session and match the id of table5 and then show data

$data=$this->db->get()->result();//all data store in $data variable

Answer 4

$this->db->select('*');
$this->db->from('blogs');
$this->db->join('comments', 'comments.id = blogs.id');
$this->db->join('authors', 'authors.id = comments.author_id');

hopefully you get my example.

Just add another $this->db->join();

For complex queries you might be better off looking at an ORM such as doctrine