Retrieve from one table only if matching column is NOT in second table

[bunner_bob]

(tried searching for this but...)

table 1 fields:
project_id
project_title
etc.

table 2 fields
invoice_id
project_id
etc.

I want to retrieve all the projects that do NOT have an invoice in the second table (i.e. projects that have never been invoiced).

Tried

SELECT projects.project_id FROM projects, invoices WHERE projects.project_id != invoices.project_id

and of course this is totally wrong (timed out). I think I need some kind of join but having trouble wrapping my head around it. All the tips tell you how to find results where there IS a match...not where there ISN'T a match.

Any advice?

Thanks!

[leatherback]

Hi,

In a similar post (here) there seems to be a solution for your problem.
Use a join to connect the two tables, and then match against non existing records.

[leatherback]

Something like:

select projects.project_id from projects 
left join invoices 
on projects.project_id = invoices.project_id 
where projects.project_id != invoices.project_id