课后作业

1.创建一个复合类型，重命名复合类型，为复合类型增加属性、删除属性

omm=# create type t_multivalues as (a int,b varchar(20));
CREATE TYPE
omm=# alter type t_multivalues rename to t_multivalues_1;
omm=# ALTER TYPE

omm=# \d t_multivalues_1
  Composite type "public.t_multivalues_1"
 Column |         Type          | Modifiers 
--------+-----------------------+-----------
 a      | integer               | 
 b      | character varying(20) | 

omm=# alter type t_multivalues_1 add attribute c int;
ALTER TYPE
omm=# alter type t_multivalues_1 drop attribute a ;
ALTER TYPE
omm=# \d t_multivalues_1
  Composite type "public.t_multivalues_1"
 Column |         Type          | Modifiers 
--------+-----------------------+-----------
 b      | character varying(20) | 
 c      | integer               | 

2.创建一个枚举类型，新增标签值，重命名标签值

omm=# create type e_multivalues as enum('first','second','third');
CREATE TYPE
omm=# 
omm=# select * from pg_enum;
 enumtypid | enumsortorder | enumlabel 
-----------+---------------+-----------
     16415 |             1 | first
     16415 |             2 | second
     16415 |             3 | third
(3 rows)

omm=# alter type e_multivalues add value if not exists 'forth';
ALTER TYPE
omm=# alter type e_multivalues rename value 'first' to 'fifth';
ALTER TYPE

3.使用新创建的类型创建表

omm=# create table tb_multivalues (id int, seq e_multivalues);
CREATE TABLE

4.删除类型

omm=# drop type t_multivalues_1;
DROP TYPE
omm=# drop type e_multivalues cascade;
NOTICE:  drop cascades to table tb_multivalues column seq
omm=# DROP TYPE