简介:在数据库中添加外键约束时,可能会遇到“Failed to add the foreign key constraint”错误。本文将探讨这个问题的原因以及如何解决它。 即刻调用文心一言能力 开通百度智能云千帆大模型平台服务自动获取1000000+免费tokens 立即体验 在数据库中添加外键约束时,你可能会遇到“Failed to add the foreign key constraint...
Cannot add foreign key constraint 问题原因 要关联的字段在要关联的表中不是主键。 解决方案 此处以tstudent表和tscore表为例说明如何解决此问题。 执行如下SQL语句,查看tstudent表结构,判断要关联的字段在要关联的表中是不是主键。 show create table tstudent; 系统显示类似如下,确认tstudent表没有主键。 执行...
A foreign key (FK) is a column or combination of columns that is used to establish and enforce a link between the data in two tables. You can create a foreign key by defining a FOREIGN KEY constraint when you create or modify a table. In a foreign key reference, a link is created ...
A FOREIGN KEY constraint does not have to be linked only to a PRIMARY KEY constraint in another table; it can also be defined to reference the columns of a UNIQUE constraint in another table. A FOREIGN KEY constraint can contain null values; however, if any column of a composite FOREIGN ...
(pymysql.err.IntegrityError) (1452, u'Cannot add or update a child row: a foreign key constraint fails 解决办法: SET FOREIGN_KEY_CHECKS = 0; # 临时取消外键约束 SET FOREIGN_KEY_CHECKS = 1; # 开启外键约束 添加之前临时取消一下外键约束,添加好数据之后,再将外键约束改回来就可以啦!
很不幸,爆出错误 “Cannot add foreign key constraint"。 问题分析: 主表与从表的外键字段类型是否保持一致 desc table 表名 主表与从表的外键字段编码是否保持一致,比如utf-8 主表与从表的外键字段存储引擎是否保持一致 通常主表字段要设置成主键,没有设置成主键,没有办法使用外键命令的。
FOREIGN KEY constraint failed code 787 This is probably due to some expectation beyond what actually can be used. e.g. as per the previous answer, you appear to be expecting objects to be updated with the respective id when the data is stored in the database. ...
我想在students表中创建外键ClassID,关联到class表中的主键ClassID上,要求级联更新删除,但创建外键过程中显示Cannot add foreign key constraint。 先看一下关联表结构, classes表结构 students表结构 出现该问题时要考虑一下几点: 1、两张表所用引擎是否一致 ...
FOREIGN KEY 约束用于预防破坏表之间连接的动作。FOREIGN KEY 约束也能防止非法数据插入外键列，因为它必须是它指向的那个表中的值之一。SQL FOREIGN KEY Constraint on CREATE TABLE 下面的 SQL 在 "Orders" 表创建时为 "Id_P" 列创建 FOREIGN KEY：MySQL:CREATE TABLE Orders (Id_O int NOT NULL,OrderNo int...
PRIMARYKEY(OrderID), FOREIGNKEY(PersonID)REFERENCESPersons(PersonID) ); SQL Server / Oracle / MS Access: CREATETABLEOrders ( OrderID intNOTNULLPRIMARYKEY, OrderNumber intNOTNULL, PersonID intFOREIGNKEYREFERENCESPersons(PersonID) ); To allow naming of aFOREIGN KEYconstraint, and for defining aFOR...