Question

I have got 2 tables: Contacts and Users.

Contacts table contains user_id which are referring to id in Users table. Contacts also contain list_type column.

Contacts: user_id, list_type
Users: id, data

How can I delete entries/rows from both tables (Contacts and Users) that are referring to given list_type?

The trick is that i don’t want to delete users who belongs to other contacts list_type.

EDIT:

Example:

Users (id,data)
1    John
2    Kate
3    Alan
4    Bob

Contacts (user_id, list_type)
1    1
3    1
1    2
4    2
2    2

Now I would like to delete list_type = 2, the result should be:

Users (id,data)
1    John - still is here, because it was also referring to list_type = 1 
3    Alan

Contacts (user_id, list_type)
1    1
3    1

Answer 1

from what i understood, i can give you this answer..
i guess users table has user_id field.. I gave this roughly, you make it comfortable to your code.. 😀

   select user_ids from contacts where list_type=some_type;

    while(resultSet.next()){
         String userid=restultSet.getString(1);
         delete from users where user_ids=userid;
    }
    delete from contacts where list_type=some_type;

EDIT:

resultSet_1 = select user_ids from contacts where list_type=some_type;  

while(resultSet_1.next()){
   String userid=resultSet_1.getString(1);
   resultSet_2 = select count(user_ids) from contacts where user_id=userid group by user_ids;
   int count=resultSet_2.getInt(1);

   if(count==1){     //if more than 1 it means contact is in more than one list_type
       delete from users where user_ids=userid;
   }
}
delete from contacts where list_type=some_type;