Question

i have a table called category in which i have main category ids and names and each main category has sub category ids and names.i also have a product table with a category id column which either has a numeric sub category id or a 2 letter main category id eg:EL for electronics..my problem is how to get top categories ie., number of products in each category in descending order.

category { sub_cat_id - numeric sub_cat_name - varchar main_cat_id - varchar (2 characters) main_cat_name } products { categoryid,//this can be either main_cat_id or sub_cat_id  } 

pls help….

Answer 1

if there is no namespace clash between main category id and sub category id, you could :

select main_cat_id , count(*) as total from category where ( main_cat_id in (select categoryid from products)                         OR         sub_cat_id in (select categoryid from products)        ) group by main_cat_id  order by total desc 

however , prima facie there seems to be a problem with the design of the category table. sub_cat should be a different table with appropriate constraints.