Want a Codeigniter Query

PHP Code:

insert into t_category (category, parent_category)
(select t1.t_category, t3.parent_id 
from t_csv t1
left join t_category t2 on t1.category = t2.category
left join t_pcategory t3 on t1.parent_category = t3.parent_category
where t2.id is null and t3.parent_category is not null) as t5 


try this query, is shoul work.  

And read about  "correlated and non correlated query" , http://www.programmerinterview.com/index...-subquery/

your query is uncorrelated, thus its much slower than correlated ones, query above is correlated. when u have 100k > rows, using uncorrelated query may take hours to finish, where correlated ones may take 1-5mins