Seth Seth - 4 months ago 17
PHP Question

Multiple Joins in Codeigniter

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 = ID, TableAId, TableBId


What I can't figure out is using active record how to make this selection. I'm trying to make as few requests as possible, but am getting stumped on how it should all be written without doing three separate calls.

Answer
$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.

Comments