Active Record substring problem

[eluser]webb_design[/eluser]
Why is the Active Record class removing multiple substrings in my query? I'm trying to do something like this:

Code:

SELECT CONCAT_WS('-', SUBSTRING(test, 1, 5), SUBSTRING(test, 6, 5)) AS testing

But it's returning this:

Code:

SELECT CONCAT_WS('-', SUBSTRING(test, 1, 5), 6, 5)) AS testing

How can I prevent this from happening?

Thanks.

UPDATE

The above is the final query, in code I'm doing this:

Code:

$this->db-select("CONCAT_WS('-', SUBSTRING(test, 1, 5), SUBSTRING(test, 6, 5)) AS testing");