CI3, active record contain $offset,$limit

Hello, i already have   model that is this 

PHP Code:

$q = $this->db->query("select * from employee where coloumnA like '%$keyword%' OR columnB like  '%$keyword%' LIMIT $offset,$limit");
return $q; 


I want to change it into query builder sentences,how to do it? I tried several times, but it gave errors.
Thanks

`$this->db->select('*')
->from('employee e')
->group_start() //this is not necessary, just added in case you will need in future. it will wrap query like statements in parentheses. there is also or_group_start()
->or_like('e.columnA', $keyword)
->or_like('e.columnB', $keyword)
->group_end()
->limit($limit, $offset);`

//added alias "e", but is not necessary

//to get results
`return $this->db->result_array(); `

//to see the generated SQL code:
`$sql = $this->db->get_compiled_select();`

It is simple query, you can figure about easily if you look in CI v3.x documentation
https://codeigniter.com/userguide3/datab...ilder.html