ON DELETE CASCADE在PostgreSQL中如何工作? 如何在PostgreSQL中创建一个触发器? 主外键关联删除(on delete set null和on delete cascade) 主外键关联,当删除的是父表数据,参照这些要删除的数据,Oracle有三种处理方式: 1、禁止删除,也是Oracle默认方法。 2、将参照要删除数据的子表对应数据置空。...对于2,需要使用...
在PostgreSQL 中,"DELETE CASCADE" 是一个用于级联删除相关记录的功能。下面是对该功能的详细解释、使用场景、设置步骤、示例以及使用时的风险和注意事项。 1. 什么是 PostgreSQL 的 "DELETE CASCADE" "DELETE CASCADE" 是一种数据库约束,用于在删除主表中的记录时自动删除与之相关联的外键表中的相关记录。这样做可...
如果删除B表中的记录,则会级联删除A表中对应记录 createtabletest(id serialprimarykey, namevarchar(10)); createtabletest01(id serialprimarykey, tidint,constraintfk_test01_tidforeignkey(tid)referencestest(id)ondeletecascade); imos=#insertintotest(name)values('a'),('b'),('c');INSERT03imos=#ins...
create table test01(id serial primary key, tid int, constraint fk_test01_tid foreign key(tid) references test(id) on delete cascade); 1. 2. imos=# insert into test(name) values('a'),('b'),('c'); INSERT 0 3 imos=# insert into test01(tid) values(1),(2),(3); INSERT 0 3...
Delete with ON DELETE CASCADEThis example demonstrates how to delete rows from a parent table and automatically delete related rows from a child table: delete_cascade.sql -- CREATE TABLE authors ( -- author_id INTEGER PRIMARY KEY, -- name VARCHAR(100) NOT NULL -- ); -- CREATE TABLE ...
How to use the PostgreSQL DELETE CASCADE to delete related rows in child tables when a parent row is deleted from the parent table.
PostgreSQL: DELETE with CASCADE The DELETE ... CASCADE operation in PostgreSQL is used to remove rows from a table and automatically delete dependent rows in other related tables. This feature is beneficial when dealing with relational databases with foreign key constraints, as it maintains referentia...
To delete data that have a foreign key relationship, you use the ON DELETE CASCADE option. Note that the DELETE statement removes data from a table but doesn’t modify the structure of the table. If you want to change the structure of a table such as removing a column, you should use ...
级联操作:对相关表执行级联操作,例如 ON DELETE CASCADE。 AFTER DELETE 触发器:如果定义了 AFTER DELETE 触发器,则会执行该触发器。 预写日志 (WAL):更改首先在行级别记录在 WAL 中,然后是索引级别的更新。 仅当事务提交后,这些更改才会成为永久更改,并可供之后启动的事务查看。但是,即使此时,数据也不会被物理...
postgresql之 drop & delete & truncate 官网:https://www.postgresql.org/docs/8.1/sql-droptable.html Name DROP TABLE -- remove a table Synopsis DROP TABLEname[, ...] [ CASCADE | RESTRICT ] Description DROP TABLEremoves tables from the database....