restrict: 同 no action,MySQL默认行为,立即检查外键约束 查询表的外键 selectconstraint_schema,constraint_schema, table_name,column_name, referenced_table_name,referenced_table_name,frominformation_schema.key_column_usagewhereconstraint_schema='cruft'and table_name='emp'and referenced_table_name='dept'; ...
altertablecourse add constraint course_id_fk foreign key (course_id) references teacher(teacher_id) on delete cascade on update cascade; PS:关联主表的column必须是索引,如果不是索引无法添加外键约束 做个测试: CSS mysql> CREATETABLEtest2 ( -> course_id INT (11) NOT NULL AUTO_INCREMENT, -> id...
云数据库MySQL是支持外键约束的,但在创建外键约束时提示如下错误。 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 ...
For information about how the MySQL implementation of foreign key constraints differs from the SQL standard, seeSection 1.7.2.3, “FOREIGN KEY Constraint Differences”. When anUPDATEorDELETEoperation affects a key value in the parent table that has matching rows in the child table, the result depe...
MySQL FOREIGN KEY ConstraintThe FOREIGN KEY constraint is used to prevent actions that would destroy links between tables.A FOREIGN KEY is a field (or collection of fields) in one table, that refers to the PRIMARY KEY in another table.
mysql> CREATE TABLE slave (cust_id int(11),cust_name int(11),cust_email char(255),cust_address char(50),PRIMARY KEY(cust_id),CONSTRAINT call_name FOREIGN KEY(cust_name) REFERENCES master(cust_id));Query OK, 0 rows affected (0.04 sec)重新创建slave数据表。注意！cust_name字段熟悉为int...
MySQL 8.0.16 より前では、CONSTRAINT symbol 句が定義されていなかった場合、または CONSTRAINT キーワードのあとにシンボルが含まれていなかった場合、InnoDB とNDB の両方のストレージエンジンは FOREIGN_KEY index_name を使用します (定義されている場合)。 MySQL 8.0.16 以上では、FOREIGN_KEY...
Mysql添加外键报错:Referencing column 'xx' and referenced column 'xx' in foreign key constraint 'xxx' are incompatible. 问题描述: 在生成迁移文件后,接着执行迁移,出现如下错误: django.db.utils.OperationalError: (3780,Referencing column 'category_id' and referenced column 'id' in foreign key ...
由于外键的存在引发的一个mysql问题 Cannot change column 'id': used in a foreign key constraint,Duplicateentry'0'forkey'PRIMARY'一查,发现表没有设置自增长。尝试增加修改表,添加自增长。ALTERTABLEsh_incentive_itemMODIFYidSMALLINTUNSIGNEDAUTO_INCREMENT;报错[
FOREIGN KEY (aref) REFERENCES first(a); Is there any restriction derived from the ADD CONSTRAINT clause? If I INSERT a row into table "second" with a value of 1234 for aref column: Is it required that at this moment a row with value 1234 MUST already exist in table "first" ?