MySQL left connection, right connection

Grades Table:

Student table:

Using an inline query in a federated query inner join similar intersection:

2, query all scores of the specified user
Select student.name,grades.* from Student,grades where student.id=grades.id and Student.name= ' AAA ';

The LEFT join returns all rows from the left table, and null to complete if there is no match in the right table.
Select Student.name,grades.math from student left join grades on student.id=grades.id;

Right joins (right query) returns all rows from the table on the left, and null-complete if there are no matches in the table

MySQL left connection, right connection