constrait mysql code example
Example 1: how to connect database foreign key in mysql
CREATE TABLE products(
productId INT AUTO_INCREMENT PRIMARY KEY,
productName varchar(100) not null,
categoryId INT NOT NULL,
CONSTRAINT fk_category
FOREIGN KEY (categoryId)
REFERENCES categories(categoryId)
ON UPDATE CASCADE
ON DELETE CASCADE
) ENGINE=INNODB;
Example 2: foreign key type uniqu mysql
mysql > create unique index index_bar_id on foos(bar_id);
mysql > alter table foos add constraint index_bar_id foreign key (bar_id) references bars (id);