Question

I’ve been hacking away at CodeIgniter for a week or so, only because I don’t have the ability to understand RoR. I’ve managed to create some rudimentary models, views and controllers but I am now at a point where I have to start considering the fact that I am using multiple models.

My question may be related to basic SQL, but I expect that there is functionality in CodeIgniter which permits returned rows from having certain data fields be replaced with information from other tables. If I knew what this concept was called in SQL, then I would at least know what to look for in the Docs, but I am only a beginner. I’d like to at least have some basic knowledge here so I can read up on the details.

For example, let’s say I have a companies table (company model) which has only two fields, an ‘id’ set as the primary key, and a ‘Company_name’ which is varchar. In addition, let’s say I have a table of stores (store model) which has four fields like ‘address’, ‘id’ (primary key), and company_id which is the index in the companies table.

The companies could be something like:

ID    Company_name
------------------------------------------------
1     CompanyA
2     CompanyB
3     CompanyC

The stores could be something like:

ID    Store_name   Address         Company_ID 
------------------------------------------------
1     StoreA       12 Main St.     1
2     StoreB       33 First Ave.   1
3     StoreC       9 Broad Rd.     2
4     StoreD       873 Wide Blvd.  3
5     StoreE       8103 Water St.  1

Where the CompanyID field relates the table back to the companies table.

If I do a basic query in CodeIgniter to return all ‘stores’ as:

$this->db->get('stores');

I will be able to go through the result row by row, but the Company_ID field will still be just an index value. Is there a way to perform a query such that the Company_ID field is automatically replaced by the appropriate company name from the companies table in the returned results? The idea would be that I want to create a resulting table which looks like the one below:

Store Name    Address           Company Name
------------------------------------------------
StoreA        12 Main St.       CompanyA
StoreB        33 First Ave.     CompanyA
StoreC        9 Broad Rd.       CompanyB
StoreD        373 Wide Blvd.    CompanyC
StoreE        8103 Water St.    CompanyA

An easy real-world example would be fast food chain stores belonging to a parent company or something like that.

Not sure how else to explain this. :/

Answer 1

What you’re looking for is a SQL join. You can do it in CodeIgniter like this.

$this->db->select("stores.Store_name, stores.Address, companies.Company_name");
$this->db->from("stores");
$this->db->join("companies", "companies.ID=stores.Company_ID");
$query = $this->db->get();

Personally, I just prefer to write the query myself.

$query = $this->db->query("select stores.Store_name, stores.Address, companies.Company_name from stores inner join companies on companies.ID=stores.Company_ID");