Re: PostgreSQL domains and NOT NULL constraint
| От | Erki Eessaar |
|---|---|
| Тема | Re: PostgreSQL domains and NOT NULL constraint |
| Дата | |
| Msg-id | AM9PR01MB8268087307B06FF1AEDC6A1BFED1A@AM9PR01MB8268.eurprd01.prod.exchangelabs.com обсуждение исходный текст |
| Ответ на | Re: PostgreSQL domains and NOT NULL constraint (Tom Lane <tgl@sss.pgh.pa.us>) |
| Список | pgsql-hackers |
>I doubt we'd consider doing anything about that.
>The whole business of domains with NOT NULL constraints
>is arguably a defect of the SQL standard, because
>there are multiple ways to produce a value that
>is NULL and yet must be considered to be of the domain type.
In my opinion it is inconsistent and illogical if a type sometimes contains a value and sometimes not.
CREATE DOMAIN d_int INTEGER NOT NULL;
All the following statements fail (and correctly so in my opinion).
SELECT (NULL)::d_int;
/*ERROR: domain d_int does not allow null values*/
SELECT Cast(NULL AS d_int);
/*ERROR: domain d_int does not allow null values*/
WITH val (v) AS (VALUES (1), (NULL))
SELECT Cast(v AS d_int) AS v
FROM Val;
/*ERROR: domain d_int does not allow null values*/ In my opinion the confusion and related problems arise from the widespread practice of sometimes treating a domain as a type (which it is not) and sometimes treating NULL as a value (which it is not).
Best regards
Erki Eessaar
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