Mysql: SELECT all items shared between two users

Question

I have two tables

item_tb

| item_id | user_id | --------------------- 

user_tb

 | user_id | user_name | ----------------------- 

In item_tb, I have many elements belonging to different user in user_tb, an element can belong to one or several users ...

, so given userid A and userid B, how can I execute the mysql query to select all elements belonging to both userA and userB?

Answer 1

  select i.item_id from item_tb i inner join user_tb u ON i.user_id = u.user_id where i.user_id IN (42, 43) group by i.item_id having count(*) = 2 

Where 42 and 43 are these users.