MySQL Create federated primary key

1. Create PRIMARY KEY syntax

ALTER TABLE table_name ADD CONSTRAINT pk_name PRIMARY KEY (column name);

2. Creating FOREIGN KEY syntax

ALTER Table news_info[child table name] ADD CONSTRAINT fk_news_info_news_type[constraint name] FOREIGN KEY (info_id) [Child table column] REFERENCES news_type[ primary table name] (ID) [Main table column];

3. Using the combined primary key

If a column cannot uniquely distinguish a table of records, consider multiple columns combined to achieve uniqueness of the table record, in the form

① when created: Create TABLE SC (
Studentno int,
CourseID int,
Score int,
Primary KEY (Studentno,courseid));

MySQL Create federated primary key