How do I write this SQL statement ?

[eluser]bEz[/eluser]
[quote author="whobutsb" date="1234929305"]For Nested Clauses like that I would just write it as a string in to the $this->db->where() method. I don't know how to write it any other way.[/quote]
Understood, a custom string would be the natural choice for such a short (overall two clause) string.

The method you provided would have required the second and third where portions to be combined with an "AND".

Code:

$this->db->where('abc.field2 = 2 AND (abc.field3 = 3 OR abc.field4 = 4)');

OR

Code:

$this->db->where('(abc.field2 = 2 AND (abc.field3 = 3 OR abc.field4 = 4))');

notice the extra set of parenthesis