Getting child node count from mysql query

Question

I'm working with a recursive table and I'm trying to build a query to get my child node counts however my query fails to return the correct count when I restrict it by the basic_user_id. The idea behind the design is to enable different users to have their own hierarchy of companies, however I can't have them conflicting with each other which is what appears to be happening.

My query

select * , count(c2.company_id ) 

from company_user c1 left join company_user c2 on c2.parent_id = c1.company_id  

where c1.company_id in (1337) 
and c1.basic_user_id = 23

group by c1.company_id;

basic_user_id = 23 should return a count of 1 which it does correctly

Now when I change basic_user_id to 541, I'm expecting it to return a count of 0 however it still seems to return a count of 1.

How do I get basic_user_id = 541 to return a count of 0 and basic_user_id = 23 to return a count of 1?

Answer 1

Could you try this? You can test here. http://www.sqlfiddle.com/#!2/73f61/2

I have added AND child_tab.basic_user_id = parent_tab.basic_user_id ON clause. Because You are doing LEFT JOIN

SELECT parent_tab.company_id, COUNT(child_tab.company_id) 
FROM company_user parent_tab LEFT JOIN company_user child_tab
    ON child_tab.parent_id = parent_tab.company_id  
      AND child_tab.basic_user_id = parent_tab.basic_user_id
WHERE parent_tab.company_id IN (1337) 
    AND parent_tab.basic_user_id = 23
GROUP BY parent_tab.company_id;

Answer 2

Resolved, I just needed to add a second join.

select * , count(c2.company_id ) 

from deepblue.company_user c1 left join deepblue.company_user c2 on c2.parent_id = c1.company_id 
and c1.basic_user_id = c2.basic_user_id 

where c1.company_id in (1337) 
and c1.basic_user_id= 541

group by c1.company_id;

Answer 3

change

count(c2.company_id ) 

to

sum(case when c2.company_id is null then 0 else 1 end) 

(please check syntax of case statement for your DB)