MYSQL One to Many
Get the Employees Managed by a Single Manager
SELECT e.emp_id , e.first_name , e.last_name FROM employees e INNER JOIN managers m ON m.mgr_id =
e.mgr_id WHERE m.mgr_id = 'M01' ;
Results in:
EMP_ID FIRST_NAME LAST_NAME
E02 Erin Macklemore
E04 Ron Sonswan
Ultimately, for every manager we query for, we will see 1 or more employees returned.
Get the Manager for a Single Employee
Consult the above example tables when looking at this example.
SELECT m.mgr_id , m.first_name , m.last_name FROM managers m INNER JOIN employees e ON e.mgr_id =
m.mgr_id WHERE e.emp_id = 'E03' ;
MGR_ID FIRST_NAME LAST_NAME
M03 Barrel Jones
As this is the inverse of the above example, we know that for every employee we query for, we will only ever see one corresponding manager.