Left outer connection: (Based on left table)
When two tables are connected, the connection conditions do not match.
Leave the data in the left table, and the data in the right table is filled with null
Example: Use the left link to take the student's data out, the student does not have the college information with null padding
Mysql> SELECT * FROM student left JOIN department
-On dept_id= d_id;
Right outer join: (The right table is the benchmark)
When connecting to two tables, when the connection condition does not match
Leave the data in the right table, and the data in the left table is filled with null
Example: Use the right outer connection to show the data of the college without
INSERT INTO department (d_name) value (' Art Institute ');
Mysql> SELECT * FROM student right Join department
-On dept_id= d_id;
MySQL Association query outer JOIN {left| Right} JOIN