Bagaimana untuk mencipta jenis datetime dalam pangkalan data MySQL

Platform sistem alam sekitar: Microsoft Windows (64-bit) 10版本：4.5

Pangkalan data Hangao menyokong menggunakan pernyataan berikut untuk mencipta jenis data yang ditentukan pengguna:

• CREATE DOMAIN: Ia mencipta jenis data yang ditentukan pengguna, yang boleh mempunyai kekangan pilihan, berdasarkan jenis asas lain, pada asasnya mentakrifkan domain.

• CREATE TYPE: Ia biasanya digunakan untuk mencipta jenis komposit (jenis data yang merupakan campuran dua atau lebih jenis data) menggunakan prosedur tersimpan.

1. Penggunaan domain dan contoh

Andaikan terdapat struktur jadual berikut:

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

Antaranya , lajur md5 Jenis dan kekangan boleh disarikan dengan mentakrifkan domain, seperti berikut:

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

2. Cipta jenis datetime dalam MySQL

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)

3. cipta penggunaan jenis dan contoh

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

Buat contoh:

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);

Atas ialah kandungan terperinci Bagaimana untuk mencipta jenis datetime dalam pangkalan data MySQL. Untuk maklumat lanjut, sila ikut artikel berkaitan lain di laman web China PHP!