当你在数据库操作中遇到“1215 cannot add foreign key constraint”这个错误时,通常意味着在尝试添加外键约束时遇到了问题。这个问题可能由多种原因引起,下面我将根据提示逐一分析并提供可能的解决方案: 确认错误发生的环境和上下文: 首先,确保你了解你正在使用的数据库系统(如MySQL、PostgreSQL等),因为不同的数据库...
SET FOREIGN_KEY_CHECKS=@OLD_FOREIGN_KEY_CHECKS; 示例: mysql> CREATE TABLE child ( -> id INT(10) NOT NULL PRIMARY KEY, -> parent_id INT(10), -> FOREIGN KEY (parent_id) REFERENCES `parent`(`id`) -> ) ENGINE INNODB; ERROR 1215 (HY000): Cannot add foreign key constraint # ...
ALTER TABLE ADD CONSTRAINT <constraint_name> <constraint_definition>;Using ALTER TABLE ADD CONSTRAINT, any of bellow constraints can be added to existing table NOT NULL CHECK UNIQUE PRIMARY KEY FOREIGN KEY Consider that you already have the following employee table.Add UNIQUE Constraint...
Cannot add foreign key constraint 错误解决办法 产生这个错误的多数原因有一下两点: 1,两张表里要设主键和外键的字段的数据类型或者数据长度不一样 (例如这个是int 另外一个是tinyint,或者都是int,但是设置的长度不同) 2,某个表里已经有记录了 3、两个表的引擎不一样,查看表的引擎语句: show table status ...
ADD CONSTRAINT post_id_fkey FOREIGN KEY (post_id) REFERENCES public.posts (id) MATCH SIMPLE ON UPDATE NO ACTION ON DELETE NO ACTION ON DELETE CASCADE NOT VALID; -- +goose Down 46 changes: 46 additions & 0 deletions 46 cmd/migrate/20241028212627_admin_user.go Original file line numberDiff...
ccu1.CONSTRAINT_NAME AND\n CONSTRAINT_TYPE = 'Foreign Key' INNER JOIN\n INFORMATION_SCHEMA.REFERENTIAL_CONSTRAINTS rc1 ON rc1.CONSTRAINT_NAME = tc1.CONSTRAINT_NAME INNER JOIN\n INFORMATION_SCHEMA.CONSTRAINT_COLUMN_USAGE ccu2 ON ccu2.CONSTRAINT_NAME = rc1.UNIQUE_CONSTRAINT_NAME\n WHERE (ccu1....
这是PostgreSQL语法中的一种令人讨厌的差距。以下是一些解决方法：
Add check constraint only to a table and not to its children. ALTER TABLE customers ADD CONSTRAINT ch_first_name CHECK (char_length(first_name) <= 20) NO INHERIT; Tutorials PostgreSQL Tutorial PostgreSQL Create Table PostgreSQL Drop Table PostgreSQL Select PostgreSQL Insert PostgreSQL Update Postgr...
postgresql and mysql are fine. However, for SQLite to use ON DELETE, we would need a new OPTIONS flag. Something like: settings.DATABASES.["default"]["OPTIONS"]["PRAGMA_foreign_keys"] = True (which would then lead to the database wrapper running the correct SQL: https://sqlite.or...
mysql添加外键报错: 1452 Cannot add or update a child row:a foreign key constraint fails 主从表的区别: 看外键在哪个表,比如外键在学生表,则学生表students为从表,班级表class为主表。 原因一: 外键字段的数据类型大小、属性(默认值),或者数据库引擎是否为InnoDB(MyISAM不支持)、编码是否一致。(外键必须...