can't write strings to database

[eluser]illuzionist[/eluser]
Hello everybody,

so I'm trying to write a string to the database and this is what I do..

I have a url just like this:
www.example.com/index.php/site/writeGPStoDatabase/?lat=45.7071587&lng=16.0575276

now what I do is I have a controller "site" and method inside called "writeGPStoDatabase", and from this method I try to write to database like this, but it won't work:

this is the code:

Code:

$locationGPS = $this->uri->segment(3);      
        
$query = 'UPDATE myTable SET time_D=current_time' . ',locationGPS=' . $locationGPS . ' WHERE id=' . $id;
$this->db->query($query);

and this code just won't work, if I change $locationGPS and put some other string it also doesn't work, it only works if I put in number values like "22002", "1113423" etc..

in SQL database locationGPS column is set to varchar(255)

TL;DR;
CI won't write strings to database if they contain letters, only if string is made up of numbers ONLY