The MySQL implementation of foreign key constraints differs from the SQL standard in the following key respects: If there are several rows in the parent table with the same referenced key value, InnoDB performs a foreign key check as if the other parent rows with the same key value do not ...
create table user( id int(10) primary key, name varchar(32) ); # 给主键重命名 # table_constraints 专门用来存储字段约束信息 create table user_id( id int(10), name varchar(32), constraint user_id_pk primary key(id) # 原来主键是id现在主键变成 user_id_pk ); 示例 mysql> desc user...
Mysql FOREIGN KEY Constraints InnoDB支持 foreign key constraints. constraint definition inInnoDBlooks like this: [CONSTRAINT [symbol]] FOREIGN KEY [index_name] (index_col_name, ...) REFERENCEStbl_name(index_col_name,...) [ON DELETEreference_option] [ON UPDATEreference_option]reference_option: ...
A table in a foreign key relationship cannot be altered to use another storage engine. To change the storage engine, you must drop any foreign key constraints first. A foreign key constraint cannot reference a virtual generated column. For information about how the MySQL implementation of foreign ...
Summary: in this tutorial, you will learn about MySQL foreign key and how to create, add, and drop foreign key constraints in MySQL. Introduction to MySQL foreign key# A foreign key is a field in a table that matches another field of another table. A foreign key places constraints on ...
MySQL Error Number 1005 Can't create table '.\homebase\user-link-cat.frm' (errno: 150) It would seem that I have a malformed set of foreign key constraints, but I can't figure how. Does anyone see my problem? Is there a way to get a more informative error message? Any assistanc...
Then add the foreign key constraints back ALTER TABLE table_name1 ADD FOREIGN KEY (table2_id) REFERENCES table2(id) ON DELETE SET NULL; ALTER TABLE tablename2 ADD FOREIGN KEY (table1_id) REFERENCES table1(id) ON DELETE SET NULL; Need a good GUI Tool for MySQL? TablePlus is a moder...
MYSQL外键(Foreign Key)的使用 在MySQL 3.23.44版本后,InnoDB引擎类型的表支持了外键约束。 外键的使用条件: 1.两个表必须是InnoDB表,MyISAM表暂时不支持外键(据说以后的版本有可能支持,但至少目前不支持); 2.外键列必须建立了索引,MySQL 4.1.2以后的版本在建立外键时会自动创建索引,但如果在较早的版本则需要...
该语法可以在CREATE TABLE和ALTER TABLE时使用,如果不指定CONSTRAINT symbol,MYSQL会自动生成一个名字。 ON DELETE、ON UPDATE表示事件触发限制,可设参数: ①RESTRICT(限制外表中的外键改动,默认值) ②CASCADE(跟随外键改动) ③SET NULL(设空值) ④SET DEFAULT(设默认值) ...
Foriengn key constraints are not working on MYSQL Innodb in Linux Fedora environment. I need help in this regard! Example script are: CREATE TABLE fiscal_year ( id INTEGER UNSIGNED NOT NULL, name VARCHAR(30) NOT NULL, start_date DATE NOT NULL, ...