inner join with empty result from right table

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

look [here also](http://stackoverflow.com/questions/367863/sql-find-records-from-one-table-which-dont-exist-in-another), the similar problem, but without accent on `joins` — rook, Aug 08 '13 at 21:54

Wirus · Accepted Answer · 2013-08-08T21:18:02.500

9

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.

edited Aug 08 '13 at 21:18

answered Aug 08 '13 at 21:11

Wirus

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10

2

+1. This is the classic "anti-join" pattern: a LEFT JOIN to find matching rows (all restaurants along with matching orders", and then a WHERE clause to eliminate restaurants that had a matching rows in orders. This is usually more efficient than an equivalent query using a `NOT IN` or `NOT EXISTS` predicate. – spencer7593 Aug 08 '13 at 21:16

score 3 · Answer 2 · answered Aug 08 '13 at 21:12

3

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'
);

answered Aug 08 '13 at 21:12

Ike Walker

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+1. the correlated subquery has a reference to an expression from the outer query. this is how it is done, though we usually (not always) get better performance with an anti-join. – spencer7593 Aug 08 '13 at 21:27
1

I use the anti-join more often myself, but I think it's useful to know both approaches. – Ike Walker Aug 08 '13 at 21:54
I agree it's useful to know both approaches, which is why I upvoted your answer. Sometimes the `NOT EXISTS` predicate is the more appropriate approach. – spencer7593 Aug 08 '13 at 22:48

Michael Goldshteyn · Answer 3 · 2013-08-08T21:17:57.683

0

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')

edited Aug 08 '13 at 21:17

answered Aug 08 '13 at 21:12

Michael Goldshteyn

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Is `id` in the subquery a reference to the `id` column in the `restaurant` table or the `order` table? Best practice dictates that column references be qualified with either a table name, or preferably, a table alias. – spencer7593 Aug 08 '13 at 21:24

inner join with empty result from right table

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