Question

我似乎无法弄清楚如何让custom domain接受NULL值。请注意，对于屎和咯咯笑，我尝试了很多不同的方法：

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，仍然没有运气......

# \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，the docs说

NULL

允许此域的值为null。这是默认值。

此子句仅用于与非标准SQL兼容   数据库。在新的应用程序中不鼓励使用它。

如果没有该条款，它仍然会说NOT NULL。

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

Answer 1

像往常一样：

在StackOverflow上发布描述性问题
在irc：//irc.freenode.net/#postgresql
让大师在几秒钟内回答问题。

11:17＆lt; RhodiumToad＆GT; EvanCarroll：它是执行它的主键 - 主键的所有列都不为空

他知道所有。

Answer 2

在这里工作（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);

输出：

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
...

如何创建接受NULL的DOMAIN？

2 个答案: