Re: Self-referential records
От | Andreas Kretschmer |
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Тема | Re: Self-referential records |
Дата | |
Msg-id | 20100124151334.GA10913@tux обсуждение исходный текст |
Ответ на | Self-referential records (Ovid <curtis_ovid_poe@yahoo.com>) |
Ответы |
Re: Self-referential records
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Список | pgsql-general |
Xi Shen <davidshen84@googlemail.com> wrote: > what if you insert other values like '1', '999'? will the insertion > successful? if so, what's the difference between a deferred reference > and no reference at all? Nice question ;-) Okay, recreate the table but without NOT NULL: test=# CREATE TABLE refers ( id SERIAL PRIMARY KEY, name VARCHAR(255) NOT NULL, parent_id INTEGER , FOREIGN KEY (parent_id)REFERENCES refers(id) deferrable initially deferred); NOTICE: CREATE TABLE will create implicit sequence "refers_id_seq" for serial column "refers.id" NOTICE: CREATE TABLE / PRIMARY KEY will create implicit index "refers_pkey" for table "refers" CREATE TABLE Zeit: 63,477 ms test=*# insert into refers (name, parent_id) values ('xxx',null); INSERT 0 1 Zeit: 0,686 ms I think, NULL is more sensible than inserting a 'random' value like 0. Andreas -- Really, I'm not out to destroy Microsoft. That will just be a completely unintentional side effect. (Linus Torvalds) "If I was god, I would recompile penguin with --enable-fly." (unknown) Kaufbach, Saxony, Germany, Europe. N 51.05082°, E 13.56889°
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