How to select users without specific one to many rows in MySQL - mysql

Question

Consider the following data set:
users table:
id (int) email (string)
1 first#example.com
2 second#example.com
order_items table:
id (int) user_id (int) generation (string)
1 1 '11'
2 1 '12'
2 1 '12.50'
3 1 '16.00'
4 2 '11'
5 2 '12'
UPDATED question
How can I select users which doesn't have order_items with generation 16.00 and have at least one order_item?
So:
email
second#example.com

Answer 1

1) Returning Users who don't have order item with generation 16 included users with no orders at all.
Assuming you have some kind of id column in order_items table:
select u.* from users u
left outer join order_items oi on (u.id = oi.user_id and oi.generation = 16)
where oi.id is null;
Otherwise use whatever primary key you have in order_items in the where condition to be NULL.
Updated to include answer for the question in comment
2) Returning users who don't have order item with generation 16 but have least one order.
select distinct u.* from users u
left outer join order_items oi16 on (u.id = oi.user_id and oi.generation = 16)
join order_items oiother on (u.id = oiother.user_id and oiother.generation != 16)
where oi16.id is null;
We do the filtering by using a second (normal) join which only returns users where it finds matching rows from the order_items table.
Here we need the distinct because the second join will multiply your rows depending on how many other orders the user have.
Alternatively you can also do a count or sum like this:
select u.*, count(distinct oiother.id) from users u
left outer join order_items oi16 on (u.id = oi.user_id and oi.generation = 16)
join order_items oiother on (u.id = oiother.user_id and oiother.generation != 16)
where oi16.id is null
group by u.id;
This will give you also how many other order items each returned user have. Or omit the count completely and using group by just to return distinct items.

Answer 2

You can use NOT EXISTS() like this:
SELECT * FROM Users u
WHERE NOT EXISTS(SELECT 1 FROM order_items o
WHERE o.userid = u.id
AND o.generation = 16)
That checks if there is a record for this user with order.generation = 16, and if there isn't it selects him.
Or not in()
SELECT * FROM Users u
WHERE u.id NOT IN(SELECT userid FROM order_items o
WHERE o.generation = 16)
That selects the list of users who have order.generation = 16, and select every id except them.

Answer 3

Following query should give you the desired output:
*update*
changed query as per the new result format in the question
As we want the data only from generation table, join with user table is not needed anymore. Here's the updated query:
select id, generation
from mytable where id not in (
select id from mytable
where generation = 16
group by id
);
Here is the SQL fiddle for it.