Question

我看上去如何获得custom域 ,以接受NUL值。关于打客和吉列斯一号船的通知,它尝试了多种不同方式:

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

但是,仍然没有任何uck......

# 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)

http://www.postgresql.org/docs/9.1/static/sql-createdomain.html” rel=“nofollow”

NUL

该领域的价值被允许为无效。这是违约行为。

This clause is only intended for compatibility with nonstandard SQL databases. Its use is discouraged in new applications.

Without the clause it still says NOT NUL.

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

Answer 1

一如既往:

Post a descriptive problem on StackOverflow
Paste link in irc://irc.freenode.net/#postgresql
Get a guru to answer question within seconds.

11:17 < Rh GodToad> Evan Carroll: 它是主要的关键所在——主要关键的所有一栏都不是无效。

他知道这一切。

Answer 2

这里的工作(第9.1页):

        -- 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);

产出:

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
...

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