這篇文章主要介紹了如何創(chuàng)建一個(gè)創(chuàng)建MySQL數(shù)據(jù)庫(kù)中的datetime類型，創(chuàng)建一個(gè)datetime類型的方法以及create domain 和create type的用法和區(qū)別,需要的朋友可以參考一下

?CREATE DOMAIN?：它創(chuàng)建了一個(gè)用戶定義的數(shù)據(jù)類型，可以有可選的約束，基于其他基本類型，實(shí)質(zhì)是定義一個(gè)域。
?CREATE TYPE?：它通常用于使用存儲(chǔ)過(guò)程創(chuàng)建復(fù)合類型(兩種或多種數(shù)據(jù)類型混合的數(shù)據(jù)類型)。

一、domain用法及示例

假如有以下表結(jié)構(gòu)：

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

其中md5列的類型及約束，可以定義一個(gè)domain來(lái)抽象，如下：

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

二、創(chuàng)建MySQL中datetime類型

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)

三、create type用法及示例

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

創(chuàng)建示例：

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);

到此這篇關(guān)于如何創(chuàng)建一個(gè)創(chuàng)建MySQL數(shù)據(jù)庫(kù)中的datetime類型的文章就介紹到這了,更多相關(guān)創(chuàng)建datetime類型內(nèi)容請(qǐng)搜索腳本之家以前的文章或繼續(xù)瀏覽下面的相關(guān)文章希望大家以后多多支持腳本之家！

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