Question

I know this is possible I just dont know how to the code or how to phrase it to search for the answer I need. I am pretty sure I need to use JOIN but again I am finding it hard to find an example to get the correct syntax.

I have 3 tables. An events table, which contains events that occur on different machines and their times. So for questions purposes events had 4 fields:

EVENTS

event_id (primary key, auto_increment)

machine_id (foreign key)

time_in

time_out

I then have a table “machines” which lists all of the machines:


MACHINES

id (key)

name

department_id (foreign key)

then lastly i have the Department table:


DEPARTMENTS

id (key)

name

I want to select all events that occur in a department. So say i want all events from events where the department_id of the machine the event occured on is = 1.

Answer 1

SELECT E.event_id, E.machine_id, E.time_in, E.time_out
FROM EVENTS E
INNER JOIN MACHINES M ON E.machine_id=M.machine_id
WHERE M.department_id = 1

By the way, if you don’t know the department id but know the name of the department, you can do an additional JOIN and use the department name:

SELECT E.event_id, E.machine_id, E.time_in, E.time_out
FROM EVENTS E
INNER JOIN MACHINES M ON E.machine_id=M.machine_id
INNER JOIN DEPARTMENTS D ON M.department_id=D.department_id
WHERE D.Name = 'Accounting'