内部联接与右表的空结果

Question

I have 2 tables, restaurants and orders, each restaurant can have many orders

restaurants table
id
name


orders table
id
restaurant_id
date

I need to find the restaurants that have no orders on some date range. In orders table I save the order dates like - each row represents one day. So, I need to make inner join, but with no results from the orders table. Say, I need to find restaurants that are free from 2013-08-09 to 2013-08-11 date range. How can I achieve this ? How to make a query, that will give the restaurants with no matching in the orders table - according to the date range ?

Actually I can do it saving all the dates in the orders table with status not_ordered, and make inner join with not_ordered = true condition, but in that case I will have to populate all the table with the dates, which is not a good thing in my case.

Thanks

Answer 1

select r.*
from restaurant r
left join orders o on r.id = o.restaurant_id and o.date between '...' and '...'
where o.id is null;

Or you can do it using not exists as shown in other answers.

Answer 2

You don't want to use an inner join for this. You can do it with an outer join, or with NOT EXISTS and a sub-query.

Here's an example of the latter approach:

select r.id,r.name 
from restaurants r 
where not exists (
  select NULL
  from orders o 
  where o.restaurant_id = r.id 
  and o.date >= '2013-08-09'
  and o.date <= '2013-08-11'
);

Answer 3

I don't know mysql very well, but this should work as general SQL:

SELECT * 
FROM restaurants 
WHERE NOT EXISTS(SELECT 1 
                 FROM order 
                 WHERE restaurant_id=id AND 
                       date BETWEEN '2013-08-09' AND '2013-08-11')