Question

Okay, I get an array with multiple user ids from a php script.

Now I have this mysql table:

+ - - - - - - - - - - - + - - - - - +
¦ fk_conversation       ¦   fk_user ¦
+ - - - - - - - - - - - + - - - - - +
¦ 1                     ¦     2     ¦
+ - - - - - - - - - - - + - - - - - +
¦ 1                     ¦     3     ¦
+ - - - - - - - - - - - + - - - - - +
¦ 1                     ¦     4     ¦
+ - - - - - - - - - - - + - - - - - +
¦ 2                     ¦     2     ¦
+ - - - - - - - - - - - + - - - - - +
¦ 2                     ¦     4     ¦
+ - - - - - - - - - - - + - - - - - +

If I get the array (2,4) I need to get the fk_conversation key = 2 but if I get the array(2,3,4) I should get the fk_conversation key = 1.

I always want to get the fk_conversation id where all connected fk_user ids are in the array.

Answer 1

select fk_conversation
from my_table
where fk_user in ( ARRAY VALUES )
and fk_conversation in (
    select fk_conversation
    from my_table
    group by fk_conversation having count(distinct fk_user) = ARRAY SIZE
)
group by fk_conversation
having count(distinct fk_user) = ARRAY SIZE;