如何创建一个创建MySQL数据库中的datetime类型

create table test_domain (id varchar,md5 text not null check(length(md5)=32));

highgo=# create domain md5 as highgo-# text not null highgo-# check ( highgo(#     length(value) = 32 highgo(# ); CREATE DOMAIN highgo=#  highgo=# \dD md5                                   List of domains  Schema | Name | Type | Collation | Nullable | Default |           Check             --------+------+------+-----------+----------+---------+----------------------------  public | md5  | text |           | not null |         | CHECK (length(VALUE) = 32) (1 row) highgo=# create table test_domain (id varchar,md5 md5); CREATE TABLE highgo=# insert into test_domain values('1','2'); ERROR:  value for domain md5 violates check constraint "md5_check" highgo=# insert into test_domain values('2','76a2173be6393254e72ffa4d6df1030a'); INSERT 0 1

highgo=# create domain datetime as timestamp without time zone; highgo=# create table t_time (id int,create_time datetime); CREATE TABLE highgo=# \d+ t_time                                      Table "public.t_time"    Column    |   Type   | Collation | Nullable | Default | Storage | Stats target | Description  -------------+----------+-----------+----------+---------+---------+--------------+-------------  id          | integer  |           |          |         | plain   |              |   create_time | datetime |           |          |         | plain   |              |  Access method: heap highgo=# insert into t_time values (1,now()),(2,now()); INSERT 0 2 highgo=#  highgo=# select * from t_time;  id |        create_time          ----+----------------------------   1 | 2021-08-03 19:28:11.207324   2 | 2021-08-03 19:28:11.207324 (2 rows)

CREATE TYPE name AS     ( [ attribute_name data_type [ COLLATE collation ] [, ... ] ] ) CREATE TYPE name AS ENUM     ( [ 'label' [, ... ] ] ) CREATE TYPE name AS RANGE (     SUBTYPE = subtype     [ , SUBTYPE_OPCLASS = subtype_operator_class ]     [ , COLLATION = collation ]     [ , CANONICAL = canonical_function ]     [ , SUBTYPE_DIFF = subtype_diff_function ] ) CREATE TYPE name (     INPUT = input_function,     OUTPUT = output_function     [ , RECEIVE = receive_function ]     [ , SEND = send_function ]     [ , TYPMOD_IN = type_modifier_input_function ]     [ , TYPMOD_OUT = type_modifier_output_function ]     [ , ANALYZE = analyze_function ]     [ , INTERNALLENGTH = { internallength | VARIABLE } ]     [ , PASSEDBYVALUE ]     [ , ALIGNMENT = alignment ]     [ , STORAGE = storage ]     [ , LIKE = like_type ]     [ , CATEGORY = category ]     [ , PREFERRED = preferred ]     [ , DEFAULT = default ]     [ , ELEMENT = element ]     [ , DELIMITER = delimiter ]     [ , COLLATABLE = collatable ] ) CREATE TYPE name

CREATE TYPE compfoo AS (f1 int, f2 text); CREATE FUNCTION getfoo() RETURNS SETOF compfoo AS $$     SELECT fooid, fooname FROM foo $$ LANGUAGE SQL; CREATE TYPE bug_status AS ENUM ('new', 'open', 'closed'); CREATE TABLE bug (     id serial,     description text,     status bug_status ); CREATE TYPE float8_range AS RANGE (subtype = float8, subtype_diff = float8mi);