MySQL为表中的每个ID选择最新的1行

Question

I have a table called sw_practice populated with organisations, and a second table called sw_invoices with the invoice data for each organisation.

Within sw_invoices, there could be several invoices (there is an incremental unique ID column) linked to the organisations with their own ID (Prac_ID).

I am trying to get a list of all organisations (whether they've been invoiced or not) but only 1 entry per organisation, so if they HAVE been invoiced, only the latest shows.

I have tried:

SELECT * FROM sw_practices as p LEFT JOIN sw_invoices as i ON p.Prac_ID = i.Prac_ID WHERE p.Active = '2' ORDER BY i.Inv_ID DESC LIMIT 1

but this only shows the latest row out of them all.

And if I remove LIMIT 1 from the end it does show all of the data but shows more than 1 entry for some organisations.

I'd like the query to say "select all from sw_practices WHERE Active = 2 and show their invoice data but only show the latest 1 for each different Prac_ID"

Answer 1

使用分组依据：

SELECT * FROM sw_practices as p LEFT JOIN (Select * FROM sw_invoices ORDER BY Prac_ID DESC )as i ON p.Prac_ID = i.Prac_ID WHERE p.Active = '2' GROUP BY p.Prac_id