如何在Oracle数据库中同时从2个表中删除？

Question

在我的Oracle数据库中，我希望从2个不同的表中删除行。

问题是，如果我先从KENNEL中删除行，那么我想在DOG表中删除的行不能删除。

以下是要从两个表中删除的SQL statements。

DELETE FROM KENNEL WHERE COUNTRY_ID IS NULL;
DELETE FROM DOG WHERE ID IN (SELECT DOG_ID FROM KENNEL WHERE COUNTRY_ID IS NULL);

如何解决此问题，以便在同时发生2次删除，并确保删除这两个表中的行？

注意：我无法从DOG中删除KENNEL，因为KENNEL是必须先删除的子记录。

Answer 1

我会将这组删除视为：

-- delete rows from child table first
DELETE FROM KENNEL WHERE COUNTRY_ID IS NULL;

-- now delete any parent rows that don't have any child records
DELETE FROM DOG WHERE ID not exists (SELECT DOG_ID FROM KENNEL);

这样做意味着如果并非所有kennel表中给定dog_id的country_ids都为null，那么您就不会尝试删除父记录 - 如果您尝试过它会出错。

Answer 2

UPDATE DOG SET [some non-key field] = 'XXX' WHERE ID IN (SELECT DOG_ID FROM KENNEL WHERE COUNTRY_ID IS NULL);

DELETE FROM KENNEL WHERE COUNTRY_ID IS NULL;

DELETE FROM DOG WHERE [non-key field] = 'XXX';