CODEWITHSUNDEEP
mysqlsqldatabaseselectdml
Brijesh Joshi
Brijesh Joshi

Reputation: 19

I have written a query and it is giving right dataset but don't know why it is not getting accepted?

The link of the question is in http://www.sql-ex.ru/learn_exercises.php#answer_ref.

The schema is

The question is to find the makers producing PCs but not laptops.

The query written by me is 

select maker
from product, pc
where product.model=pc.model
and maker not in
(
  select maker
  from product,laptop
  where product.model=laptop.model
 )

And the message I am getting is

Your query returned the correct dataset on the first (available) database, but it returned incorrect dataset on the second checking database.

Upvotes: 0

Views: 81

Answers (1)

Yogesh Sharma
Yogesh Sharma

Reputation: 50163

You can do join with not exists :

select distinct p.maker
from product p inner join
     pc
     on pc.model = p.model 
where not exists (select 1 from laptop l where l.model = p.model);

However, join will produce duplicate rows if pc table has duplicate rows. So, you can use exists instead :

select p.maker
from product p
where exists (select 1 from pc where pc.model = p.model) and
      not exists (select 1 from laptop l where l.model = p.model);

Upvotes: 0

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