将以下 MySQL 查询转换为 codeigniter

Question

How to write this query in codeigniter

SELECT U.username,U.user_id
FROM storylikes S, user U
WHERE U.user_id=S.user_id_fk AND S.user_id_fk='$id'

Answer 1

try this :

$this->db->select('u.username, u.user_id');
db->where('u. user_id = s.user_id_fk');
$this->db->where('s.user_id_fk = '.$id);
$query = $this->db->get('storylikes s, user u');

use $your_variable = $query->result(); for the result

Answer 2

you should use joins instead of this query

$this->db->select('username,user_id');
$this->db->from('user');
$this->db->join('storylike','storylike.user_id_fk = user.user_id');
$this->db->where('storylike.user_id','$id');

Answer 3

as long as the db helper is loaded... You dont need to do anything special

$query = $this->db->query('SELECT U.username,U.user_id FROM storylikes S, user U WHERE U.user_id=S.user_id_fk AND S.user_id_fk=$id);

Using a cartesian (cross join) by doing FROM with 2 tables can cause some unruly results if not used 'correctly'

I suggest that if you are trying to just join tables together your SQL should be

SELECT U.username,U.user_id 
FROM storylikes S, user U 
INNER JOIN user U ON S.user_id = U.user_id_fk
WHERE S.user_id_fk=$id

CI querybuilder for this would be:

$query = $this->db->select('U.username,U.user_id')
    ->join('user U', 'S.user_id = U.user_id_fk', 'inner')
    ->where('S.user_id', $id)
    ->get('user U');

Using the correct join for the correct requirements is key;

1. INNER JOIN to ensure both FROM and the JOIN table match 1 for 1...
2. LEFT JOIN if you want to ensure you have all data from your FROM table and any without results in the JOIN table show up as NULL
3. RIGHT JOIN (opposite of left), to grab all data from the JOIN table and only matching data from the FROM table.
4. CROSS (CARTESIAN) JOIN when you want to ... frankly... mash the data together... A CROSS JOIN will also function like an INNER JOIN when you stipulate criteria in the WHERE statement (like you did) but still, use the correct JOIN for the correct usage-case.

There are other available joins but those are the basics.