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...
报错信息如下: (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...
[constraint] [外键名称] foreign key (外键字段名) references 主表 (主表列名) ); alter table 表名 add constraint 外键名称 foreign key (外键字段名) references 主表 (主表列名); 例如: alter table emp add constraint fk_emp_dept_id foreign key (dept_id) references dept(id); 很不幸,爆出错误...
mysql>CREATETABLEtb_emp6->(->idINT(11)PRIMARYKEY,->nameVARCHAR(25),->deptIdINT(11),->salaryFLOAT,->CONSTRAINTfk_emp_dept1->FOREIGNKEY(deptId)REFERENCEStb_dept1(id)->); Query OK,0rows affected (0.37sec) mysql>DESCtb_emp6;+---+---+---+---+---+---+|Field|Type|Null|Key|Def...
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 ...
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 ...
PT.COLUMN_NAMEASPrimaryKeyColumnFROMINFORMATION_SCHEMA.REFERENTIAL_CONSTRAINTS FKINNERJOININFORMATION_SCHEMA.KEY_COLUMN_USAGE CUONFK.CONSTRAINT_NAME=CU.CONSTRAINT_NAMEINNERJOININFORMATION_SCHEMA.KEY_COLUMN_USAGE PTONFK.UNIQUE_CONSTRAINT_NAME=PT.CONSTRAINT_NAMEWHEREPK.TABLE_NAME='YourTableName';-- 替换为你...
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 ...
MySQL如何设置外键约束cannot add foreign key constraint设置外键约束失败原因,程序员大本营,技术文章内容聚合第一站。
INFORMATION_SCHEMA.KEY_COLUMN_USAGE WHERE CONSTRAINT_SCHEMA = 'ycapp_uat' AND REFERENCED_TABLE_NAME = 'act_re_deployment'; 可以发现act_re_model的外键列deployment_id_关联act_re_deployment的主键列ID_ 2、查看act_re_model表 可以发现act_re_model表已经有数据了,但act_re_deployment都没创建,那就是...