How to use Navicat to create an associated primary foreign key for two tables

First, understand the definition of primary and foreign keys

Primary key ： It's the only way to identify a record , There can be no repetition , Not allowed to be empty , To ensure data integrity .

Foreign keys ： Is the primary key of another table , Foreign keys can have duplicate , It can be null , Used to make connections with other tables . So when it comes to foreign keys , It must involve at least two tables .

For example, department table and employee table ：

Id=Dept_id, and Dept_id Is the foreign key in the employee table ： Because the employees in the employee table need to know which department they belong to , You can use foreign keys Dept_id Find the corresponding department , Then you can find various field information in the Department table , So that the two tables are related . So , Foreign keys must be created from tables , So as to find the connection with the main table ; From the table is responsible for maintaining the relationship between the two .

The next in Navicat Set foreign keys inside

First step ： Check the configuration

Interview questions ： What storage engine does your database use ？ The difference is that ？

answer ： Common are MyISAM and InnoDB.
MyISAM： Foreign key constraints are not supported . Unsupported transaction . When mass importing data , It will insert data and build indexes at the same time , So in order to improve execution efficiency , You should disable indexing first , Open the index after the full import .
InnoDB： Support for foreign key constraints , Support transactions . Indexes are handled separately , No reference index required .

The second step ： Create an index for the column corresponding to the foreign key

After completing the above configuration, start to set the foreign key ！

RESTRICT( Limit )： If you want to delete the main table , Below it, there are records corresponding to the slave table , This master table will not be deleted .
CASCADE（ cascade ）： If the record of the main table is deleted , The associated records in the table will be deleted .

thus , The association between the two tables has been established ！