CREATE DOMAIN

NAME
SYNOPSIS
DESCRIPTION æè¿°
PARAMETERS åæ°
EXAMPLES ä¾å
COMPATIBILITY å¼å®¹æ§
SEE ALSO åè§
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NAME

CREATE DOMAIN - å®ä¹ä¸ä¸ªæ°å

SYNOPSIS

CREATE DOMAIN name [AS] data_type
[ DEFAULT expression ]
[ constraint [ ... ] ]

where constraint is:

[ CONSTRAINT constraint_name ]
{ NOT NULL | NULL | CHECK (expression) }

DESCRIPTION æè¿°

CREATE DOMAIN å建ä¸ä¸ªæ°çæ°æ®åã å®ä¹åçç¨æ·æ为å¶ææèã

å¦æç»åºä¸ä¸ªæ¨¡å¼å称ï¼æ¯å¦ï¼CREATE DOMAIN myschema.mydomain ...ï¼ï¼ é£ä¹è¯¥åæ¯å¨æå®ç模å¼ä¸å建çãå¦åå®ä¼å¨å½å模å¼ä¸å建ã ååå- å¿éå¨å¶æå¨æ¨¡å¼ä¸çç°æç±»åååä¸å¯ä¸ã

åå¯ä»¥ä¾¿äºæ们æä¸å表ä¹é´çå¬å±åæ½åå°ä¸ä¸ªä½ç½®è¿è¡ç»´æ¤ã æ¯å¦ï¼ä¸ä¸ªçµåé®ä»¶å°åå段å¯è½å¨å¤ä¸ªè¡¨ä¸ä½¿ç¨ï¼ææçé½æ¯åæ ·çå±æ§ã æ们å¯ä»¥å®ä¹å¹¶ä½¿ç¨ä¸ä¸ªåï¼èä¸æ¯åå«è®¾ç½®æ¯ä¸ªè¡¨ç约æã

PARAMETERS åæ°

name

è¦å建çåååï¼å¯ä»¥æ模å¼ä¿®é¥°ï¼ã

data_type

åçä¸å±æ°æ®ç±»åãå®å¯ä»¥åå«æ°ç»å£°æåã

DEFAULT expression

DEFAULT åå¥ä¸ºåæ°æ®ç±»åçå段声æä¸ä¸ªç¼ºçå¼ã 该å¼æ¯ä»»ä½ä¸å«åéç表达å¼ï¼ä½ä¸å许åæ¥è¯¢ï¼ã 缺ç表达å¼çæ°æ®ç±»åå¿éå¹éåçæ°æ®ç±»åãå¦æ没æ声æ缺çå¼ï¼ é£ä¹ç¼ºçå¼å°±æ¯ç©ºå¼ã

缺ç表达å¼å°ç¨å¨ä»»ä½ä¸ä¸ºè¯¥å段声ææ°å¼çæå¥æä½ã å¦æ为ç¹å®çå段声æäºç¼ºçå¼ï¼é£ä¹å®è¦çä»»ä½å该åç¸å³èç缺çå¼ã ç¶åï¼åç缺çè¦çä»»ä½ä¸ä¸å±æ°æ®ç±»åç¸å³ç缺çã

CONSTRAINT constraint_name

ä¸ä¸ªçº¦æçå¯éå称ãå¦æ没æ声æï¼ç³»ç»çæä¸ä¸ªååã

NOT NULL

è¿ä¸ªåçæ°å¼ä¸å许为 NULLã

NULL

è¿ä¸ªåçæ°å¼å许为空ãå®æ¯ç¼ºçã

è¿ä¸ªåå¥åªæ¯ç¨äºåéæ åç SQL æ°æ®åºå¼å®¹ç¨ã æ们ä¸å»ºè®®å¨æ°çåºç¨ä¸ä½¿ç¨å®ã

CHECK (expression)

CHECK åå¥å£°æå®æ´æ§çº¦ææèæ¯æµè¯ï¼åå°æ°å¼å¿é¡»æ»¡è¶³è¿äºè¦æ±ã æ¯ä¸ªçº¦æå¿é¡»æ¯ä¸ä¸ªçæä¸ä¸ªå¸å°ç»æç表达å¼ãå®åºè¯¥ä½¿ç¨åå VALUE æ¥å¼ç¨è¢«æµè¯çæ°å¼ã

ç®åï¼CHECK 表达å¼ä¸è½åå«åæ¥è¯¢ï¼ä¹ä¸è½å¼ç¨é¤ VALUE ä¹å¤çåéã

EXAMPLES ä¾å

è¿ä¸ªä¾ååå»ºäº country_code æ°æ®ç±»å并ä¸å¨ä¸ä¸ªè¡¨å®ä¹ä¸- 使ç¨äºè¯¥ç±»åï¼

CREATE DOMAIN country_code char(2) NOT NULL;
CREATE TABLE countrylist (id integer, country country_code);

COMPATIBILITY å¼å®¹æ§

CREATE DOMAIN å½ä»¤ç¬¦å SQL æ åã

SEE ALSO åè§

DROP DOMAIN [drop_domain(7)]

è¯è

Postgresql ä¸æç½ç« ä½ä¼å¹³ <laser@pgsqldb.org>

è·

æ¬é¡µé¢ä¸æçç±ä¸æ man æå页计åæä¾ã
ä¸æ man æå页计åï¼https://github.com/man-pages-zh/manpages-zh

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