Postgres中的ON DELETE SET NULL [英] ON DELETE SET NULL in postgres

问题描述

我是Postgresql环境的新手，所以迷路了一段时间。父实体删除后，我想保留数据。我想知道如何为postgresql数据库设置 ON DELETE SET NULL。请给我一个提示。

HI I'm new to postgresql environment so been lost for a while. I want to keep my data when parent entity is deleted. I want to know how to make 'ON DELETE SET NULL' for postgresql database. Please give me a clue.

推荐答案

ON DELETE SET NULL 是一个标准外键约束选项。

ON DELETE SET NULL is a standard foreign key constraint option.

CREATE TABLE some_child (
    parent_id integer references parent(id) on delete set null
);

或：

ALTER TABLE some_child 
ADD CONSTRAINT parent_id_fk 
FOREIGN KEY (parent_id) REFERENCES parent(id) 
ON DELETE SET NULL;

请参见文档。

在以后的文章中，请确保您包括PostgreSQL版本并说明您已经尝试过的内容。

In future posts make sure you include your PostgreSQL version and explain what you've already tried.

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