sql select all if column has only two particular values - mysql

Question

orders (
o_id INT AUTO_INCREMENT,
o_status TINYINT,
o_description VARCHAR(50),
)
orders_products (
op_id INT AUTO_INCREMENT,
op_order_id INT(11),
op_product_id INT(11),
op_price DECIMAL(19, 2),
)
How to select all orders that have ONLY products with id = 1 and id = 2.
Thank you and sorry from my English...

Answer 1

There are different ways to get the desired result, this utilizes conditional aggregation:
select *
from orders
where o_id in
(
select op_order_id
from orders_products
having count(case when op_product_id = 1 then 1 end) > 0 -- at least one row with 1
and count(case when op_product_id = 2 then 1 end) > 0 -- at least one row with 2
and count(case when op_product_id not in (1,2) then 1 end) = 0 -- no other value
)
Depending on indexes/selectivity EXISTS/NOT EXISTS might be faster:
select o_id
from orders as o
where exists (select *
from orders_products as op
where op.op_order_id = o.o_id
and op.op_product_id = 1) -- at least one row with 1
and exists (select *
from orders_products as op
where op.op_order_id = o.o_id
and op.op_product_id = 2) -- at least one row with 2
and not exists (select *
from orders_products as op
where op.op_order_id = o.o_id
and op.op_product_id not in (1,2)) -- no other value

Answer 2

You could first find all the distinct order and product combination for product 1 or 2 or both, and then look for orders that have both.
create table orders (o_id INT);
create table orders_products (op_order_id INT(11), op_product_id INT(11));
insert into orders values (1), (2);
insert into orders_products values (1, 1), (1, 2), (2, 2);
select o_id from (
select distinct o_id, op_product_id
from orders o
inner join orders_products op on op.op_order_id = o.o_id
where op.op_product_id in (1,2)
) main
group by o_id
having count(*) = 2
Result:
1
Another way to write the query could be like this:
select o_id
from orders o
where exists (select 1 from orders_products where op_order_id = o.o_id and op_product_id = 1)
and exists (select 1 from orders_products where op_order_id = o.o_id and op_product_id = 2)

Answer 3

I would do this using aggregation and having:
select order_id
from order_products op
group by order_id
having sum(product_id = 1) > 0 and
sum(product_id = 2) > 0 and
sum(product_id not in (1, 2)) = 0;
If you want additional information about the order, then just join in the orders table.
Your question is what I call a "set-within-set" query . . . looking for patterns in a hierarchy (that is products within an order). There are several ways to solve this, but the having clause turns out to be quite general.