WebJun 10, 2024 · MySQL创建外键时,总是会遇到这样的报错:Cannot add foreign key constraint,有时觉得不明所以,摸不着头脑。 报错信息表示创建外键失败,应该从以下两个方面来检查: 1)设置的外键字段一定不 … WebFeb 27, 2024 · mysql中添加外键约束遇到一下情况:cannot add foreign key constraint出现这个问题一般是开发工作者对外键的使用出现了疏忽,我们先清晰一下外键的使用:外键字段不能为该表的主键;外键字段参考字段必须为参考表的主键。如果出现”cannot add foreign key constraint”的情况,建议先检查一下,主表是否有 ...
SQL FOREIGN KEY - W3Schools
WebJul 12, 2016 · Navicat 关联表创建外键 1215 Cannot add foreign key constraint 创建外键报错,1215 connot add foreign key constraint。 报错原因 主从表引擎不一致,只有InnoDB支持外键,所以主从表的引擎都设置为InnoDB。 主从表关联字段的类型与长度不一致,所以请查看下字段类型与长度是否一致。 WebJun 7, 2024 · CONSTRAINT fk_user_in_org__org_roles1 FOREIGN KEY (`role`) REFERENCES students.org_roles(`label`) You need a index on the table org_roles for the column label CREATE TABLE IF NOT EXISTS students.org_roles ( `org_id` INT NOT NULL, `label` VARCHAR(32) NOT NULL, KEy (`label`), PRIMARY KEY (`org_id`, … chronic kidney disease risks
MySQL报错cannot add foreign key constraint解决方法_滴 …
WebSep 21, 2013 · The syntax of FOREIGN KEY for CREATE TABLE is structured as follows:. FOREIGN KEY (index_col_name) REFERENCES table_name (index_col_name,...) So your MySQL DDL should be: create table course ( course_id varchar(7), title varchar(50), dept_name varchar(20), credits numeric(2 , 0 ), primary key (course_id), FOREIGN KEY … WebJan 22, 2016 · When you are implementing one-to-one relationship or composite primary key you may use foreign key as a primary key in your child table. Definition of foreign key should not define as ON DELETE SET NULL. Since primary key cannot be NULL. The following example will illustrate this case better: WebApr 6, 2024 · 6) The foreign key is a multi-column PK or UK, where the referenced column is not the leftmost one. How to diagnose: Do a SHOW CREATE TABLE parent to check if the REFERENCES part points to a column that is present in some multi-column index(es) but is not the leftmost one in its definition. How to fix: Add an index on the parent table … chronic kidney disease stage