MySQL select 同组id的所有行

Question

I'm using using MySql 5.7.18 and PHP 7.

I have this table:

id | object_id | item_id
-------------------------
1       1          2
2       1          3
3       1          4

4       2          5
5       2          3

6       3          2
7       3          3
8       3          4

9       4          2

10      5          1
11      5          3
12      5          5

13      6          2
14      6          3
15      6          4

So I need to select the reference object by id, for example I'll take the object_id 1 and take his items, so in my code I'll get:

$object_id = 1;
$item_ids = [2, 3, 4];

Now I want to get all object_id who have the same group of item_id . So here I need to get the object_id 3 and 6 because all of them have the same item_id than the object 1.

Another example if I have the object_id 2 in reference I'll get no result because there are no row with the same group ids.

It is possible to do that with SQL query or I have to do it in my code?

Answer 1

Yes it seems possible by concatenation, here it is:

select a.* from (
    select object_id, group_concat(item_id order by id separator '-') as item_list 
    from test group by object_id
) a where a.item_list = '2-3-4'

Here's the fiddle:

http://sqlfiddle.com/#!9/6360bc/6

---

If you want to query by object ID:

select a.* from (
    select object_id, group_concat(item_id order by id separator '-') as item_list 
    from test group by object_id
) a where a.item_list = (
    select group_concat(item_id order by id separator '-') 
    from test where object_id = 1
)