如何創建一個接受NULL的DOMAIN？

Question

我似乎無法弄清楚如何讓custom domain接受NULL值。請注意，對於媽和笑聲我已經嘗試了很多不同的方法：

DROP SCHEMA census CASCADE; 
CREATE SCHEMA census; 
-- FIRST FOUR METHODS: NULL before CHECK, in CHECK, and NULL after CHECK 
CREATE DOMAIN census.sex AS text NULL CHECK (VALUE IN ('M', 'F', 'NULL') OR VALUE IS NULL) NULL; 
CREATE TABLE census.names (
    name  text 
    , freq  int 
    , cumfreq float 
    , rank  float 
    , is_last bool 
    , sex  census.sex NULL -- fourth way 
    , PRIMARY KEY (is_last, sex, name) 
); 

但是，仍然沒有運氣...

# \d census.names; 
      Table "census.names" 
Column |  Type  | Modifiers 
---------+------------------+----------- 
name | text    | not null 
freq | integer   | 
cumfreq | double precision | 
rank | double precision | 
is_last | boolean   | not null 
sex  | census.sex  | not null 
Indexes: 
    "names_pkey" PRIMARY KEY, btree (is_last, sex, name) 

更有趣的是，the docs說

NULL

該域的值允許爲空。這是默認設置。

本節僅用於與非標準SQL 數據庫的兼容性。新應用中不鼓勵使用它。

沒有條款，它仍然說NOT NULL。

$ psql --version 
psql (PostgreSQL) 9.1.1 
contains support for command-line editing 

Answer 1

像往常一樣：

1. 後在計算器上的描述性問題IRC
2. 粘貼鏈接：//irc.freenode.net/#postgresql
3. 獲得一個大師到內回答問題秒。

11:17 < RhodiumToad> EvanCarroll：它的主鍵，做它 - 一個主鍵的所有列不爲空

他知道一切。這裏

Answer 2

工程（第9.1）：

 -- Domain with only values 1 ... 9 allowed, 
     -- used for both the {x,y,z} coordinates and the cell values. 
CREATE DOMAIN one_nine 
     AS INTEGER 
     CHECK (value >= 1 AND value <= 9) 
     ; 

CREATE DOMAIN one_nine_notnull 
     AS INTEGER NOT NULL 
     CHECK (value >= 1 AND value <= 9) 
     ; 

CREATE TABLE all_numbers 
     (val one_nine_notnull PRIMARY KEY 
     ); 
INSERT INTO all_numbers(val) 
SELECT nn FROM generate_series(1,9) AS nn; 

     -- Table containing exactly one sudoku puzzle. 
     -- The zzz coordinate (the "box number") is formally redundant 
     -- (since it is functionally dependant on {xxx,yyy}) 
DROP TABLE IF EXISTS sudoku3 CASCADE; 
CREATE TABLE sudoku3 
     (yyy one_nine_notnull 
     , xxx one_nine_notnull 
     , zzz one_nine_notnull 
     , val one_nine 
     ); 
INSERT INTO sudoku3 (yyy,xxx,zzz,val) VALUES (NULL, 3, 1, 4); 
INSERT INTO sudoku3 (yyy,xxx,zzz,val) VALUES (1, 3, 1, 14); 

     -- Conveniance view with 3-width horizontal and vertical bands 
CREATE VIEW v_sudoku AS (
     SELECT yyy,xxx,zzz 
     , val 
     , (xxx+2)/ 3 as x3 
     , (yyy+2)/ 3 as y3 
     FROM sudoku3 
     ) 
     ; 

     -- First constraint: (x,y) is unique 
ALTER TABLE sudoku3 ADD PRIMARY KEY (xxx,yyy); 

     -- Three constraints for unique values for {rows,columns,boxes} 
CREATE UNIQUE INDEX sudoku_xv ON sudoku3 (xxx,val); 
CREATE UNIQUE INDEX sudoku_yv ON sudoku3 (yyy,val); 
CREATE UNIQUE INDEX sudoku_zv ON sudoku3 (zzz,val); 

輸出：

drop cascades to type w00t.one_nine_notnull 
drop cascades to table w00t.all_numbers 
drop cascades to table w00t.sudoku3 
drop cascades to view w00t.v_sudoku 
drop cascades to view w00t.sudoku_row 
drop cascades to view w00t.valid_moves 
drop cascades to view w00t.low_hanging_fruit 
drop cascades to view w00t.magic_moves 
drop cascades to function w00t.sudoku_magic() 
DROP SCHEMA 
CREATE SCHEMA 
SET 
CREATE DOMAIN 
CREATE DOMAIN 
NOTICE: CREATE TABLE/PRIMARY KEY will create implicit index "all_numbers_pkey" for table "all_numbers" 
CREATE TABLE 
INSERT 0 9 
NOTICE: table "sudoku3" does not exist, skipping 
DROP TABLE 
CREATE TABLE 
ERROR: domain one_nine_notnull does not allow null values 
ERROR: value for domain one_nine violates check constraint "one_nine_check" 
CREATE VIEW 
NOTICE: ALTER TABLE/ADD PRIMARY KEY will create implicit index "sudoku3_pkey" for table "sudoku3" 
ALTER TABLE 
CREATE INDEX 
CREATE INDEX 
CREATE INDEX 
INSERT 0 81 
...