mysql foreign key example

The meaning of the properties in the MySQL foreign key setting:Cascade WaySynchronize update/delete out a matching record of a child table when Update/delete records on the parent tableSet NULL modeSet the column of the matching record on the child table to NULL when the record is update/delete on the parent tableNote that the

8. Add a FOREIGN keyMysql>alter table tb_product Add constraint fk_1 foreign key (Factoryid) references tb_factory (Factoryid);mysql> ALTER TABLE 9. Delete foreign keysMysql>alter table tb_people drop foreign

MySQL Restart command:Redirecting To/bin/systemctl Stop Mysqld.service[Email protected] centos7share]# systemctl start Mysqld.service[Email protected] centos7share]# mysql-uroot-proot123MySQL Run SQL file: Source/mnt/hgfs/xxx.sql;Failed to initialize the foreign Key association caused by SQL run:: 35:31.428 ERROR jdbc.

Environment: MySQL Server 5.1 + Navicat for MySQL 8.2 Problem: 121 error occurred while modifying foreign key deletion Solve: Change the foreign key name to another name. Error message Reference: Error 121 This is the name

In MySQL, you cannot delete a table and modify the table structure if a FOREIGN key constraint is established between the table and the table. The workaround is to cancel the foreign key constraint in MySQL: SET foreign_key_checks

Tags: img Images logs src nbsp Reference primary key Foreign field nameA foreign key is a field in a table that may not be the primary key of the table, but corresponds to the primary key of another table.Primary table (parent tab

A scenario appears:ica_classify The primary key ica_classify_id in the table is the foreign key of the website_commodity_information tableTable structure slightlyFOREIGN KEY constraint error when inserting data into table website_commodity_information using MyBatis# # # Error updating database. Cause:com.mysql.jdbc.exc

. Cascade ModeSynchronize update/delete out a matching record of a child table when Update/delete records on the parent table. Set Null methodSet the column of the matching record on the child table to NULL when the record is update/delete on the parent tableNote that the foreign key column of the child table cannot be not NULL. No Action ModeIf there are matching records in the child table, the Update/dele

Tags: nbsp GPO body Blog Get simple technology share first step userReprint: http://blog.csdn.net/u013215018/article/details/54981216Now there are two tables, one is the roles table (the role table), the other is the Roleuser table (user role)Now I want to set the Roleid property in the Roleuser table to a foreign key, associating the Roleid property in the Roles table.Operation Steps:The first step:Step Tw

Tags: sp on bs SQL MySQL CA server nbsp dateBackground:You know that when you define a foreign key, you are given an on delete ... on update ...;What is specified here is how the columns of the table should be changed to cater for the changes in the columns of the main table. The value of indexing from a foreign

Dead lockexists in row level lockConditions of existence1. Resources can only be occupied by one thread at a time2. Resource possession cannot be forcibly deprived3. Request and maintain possession (to maintain the possession of existing resources while requesting possession of resources)4, the death cycle (generally do the program of the people most concerned about the point)One to three points is MySQL InnoDB all the features, only four is what we c

SQL FOREIGN key Foreign Key instance tutorial The key constraints of foreign SQLThe foreign key is at one table point and the primary

record can only be connected to one record of another table, or one-to-many, and a table record is connected to multiple records from another table. The definition of "key" and "index" in MySQL is the same, so the foreign key and the primary key are also one of the indexes.

allowed. SQL> update prim set v_id = 4 where v_id = 2; Update prim set v_id = 4 where v_id = 2 ORA-02292: violation of the complete constraints (A. FK_CHILD_PRIM)-subrecord found SQL> update child set v_id = 5 where v_id = 2; Update child set v_id = 5 where v_id = 2 ORA-02291: violating the complete constraint condition (A. FK_CHILD_PRIM)-parent keyword not found On delete cascade is called "Cascading deletion". It is a convenient policy for developers to directly "Ignore" sub-records and dele

First look at the definitions of the various keys: Super Key: An attribute set that uniquely identifies a tuple in a relationship is called a super key for a relational pattern candidate Keys (Candidate key): A key that does not contain extra attributes is called a candidate key