aTL6hz3Z

1CREATE TABLE userdata (
2  userid integer,
3  userdataid integer,
4  info char(200)
5  primary key (userid, userdataid)
6);
7	
8DROP TABLE IF EXISTS `test`.`animals`;
9CREATE TABLE  `test`.`animals` (
10  `grp` char(30) NOT NULL,
11  `id` mediumint(9) NOT NULL AUTO_INCREMENT,
12  `name` char(30) NOT NULL,
13  PRIMARY KEY (`grp`,`id`)
14) ENGINE=MyISAM;
15
16INSERT INTO animals (grp,name) VALUES
17    ('mammal','dog'),('mammal','cat'),
18    ('bird','penguin'),('fish','lax'),('mammal','whale'),
19    ('bird','ostrich');
20
21SELECT * FROM animals ORDER BY grp,id;
22
23Which returns:
24
25+--------+----+---------+
26| grp    | id | name    |
27+--------+----+---------+
28| fish   |  1 | lax     |
29| mammal |  1 | dog     |
30| mammal |  2 | cat     |
31| mammal |  3 | whale   |
32| bird   |  1 | penguin |
33| bird   |  2 | ostrich |
34+--------+----+---------+
35	
36mysql> create table foo (
37  id int primary key auto_increment, 
38  id2 int auto_increment
39);
40ERROR 1075 (42000): Incorrect table definition; 
41there can be only one auto column and it must be defined as a key
42	
43Person(id, name, email, street, zip_code, area)
44	
45Person(id, name, email, street, zip_code)
46Area(zip_code, name)