Lecho <[EMAIL PROTECTED]> writes:
>I have a db with objects table, each of those objects may belong to groups
>of objects. The number of groups can be about 256 and an object
>belongs from one to many different groups at once.
Lecho,
I threw together the following tables/data/queries that I believe
handle your setup:
create table objs (
obj_id int,
obj_name varchar(20)
);
create table grps (
grp_id int,
grp_desc varchar(20)
);
create table grp_map (
obj_id int,
grp_id int
);
insert into objs (obj_id, obj_name) values (1, 'Obj1');
insert into objs (obj_id, obj_name) values (2, 'Obj2');
insert into objs (obj_id, obj_name) values (3, 'Obj3');
insert into objs (obj_id, obj_name) values (4, 'Obj4');
insert into grps (grp_id, grp_desc) values (10, 'Grp10');
insert into grps (grp_id, grp_desc) values (20, 'Grp20');
insert into grps (grp_id, grp_desc) values (30, 'Grp30');
insert into grp_map (obj_id, grp_id) values (1, 10);
insert into grp_map (obj_id, grp_id) values (1, 30);
insert into grp_map (obj_id, grp_id) values (2, 20);
insert into grp_map (obj_id, grp_id) values (2, 30);
insert into grp_map (obj_id, grp_id) values (3, 10);
insert into grp_map (obj_id, grp_id) values (3, 20);
insert into grp_map (obj_id, grp_id) values (3, 30);
insert into grp_map (obj_id, grp_id) values (4, 30);
select distinct(obj_id) from grp_map
where grp_id in (10, 20);
mysql> select distinct(obj_id) from grp_map
-> where grp_id in (10, 20)
-> ;
+--------+
| obj_id |
+--------+
| 1 |
| 2 |
| 3 |
+--------+
3 rows in set (0.00 sec)
This will tell you all the objects that belong to groups 10 or 20
Brad Eacker ([EMAIL PROTECTED])
--
MySQL General Mailing List
For list archives: http://lists.mysql.com/mysql
To unsubscribe: http://lists.mysql.com/[EMAIL PROTECTED]
