Foreign key

Method 1 - while creating table

create table if not exists `student`(
key `fk_gradeId` (`gradeId`), -- define key
constraint `fk_gradeId` foreign key (`gradeId`) references `grade` (`gradeId`) -- add constranit + reference
  )

Method 2 - after create table

alter table `students` 
add constraint `fk_gradeId` foreign key(`gradeId`) references `grade` (`gradeId`)

The above two methods are physical foreign keys, database-level foreign keys, which are not recommended

Best practice

• Database is only used to store data

• Using foreign keys by programming