This will get all results from table 1 where they appear in table 2, and get the highest ID of that result, and display the data!
SELECT * FROM table1
INNER JOIN ( SELECT MAX(table1.id) AS id FROM table1
INNER JOIN
table2 ON table2.client = table1.client
AND table2.campaign=table1.campaign
AND table2.enabled != 'disabled'
GROUP BY table1.client, table1.campaign )
AS m ON m.id = table1.id
Another version using WHERE and AND
SELECT * FROM mydata
INNER JOIN ( SELECT MAX(mydata.id) AS id FROM mydata
INNER JOIN
targets ON targets.client = mydata.client
AND targets.campaign=mydata.campaign
WHERE mydata.date='$thisday'
AND mydata.client ='$boardname'
AND targets.enabled != 'disabled'
GROUP BY mydata.client, mydata.campaign )
AS m ON m.id = mydata.id
order by mydata.campaign ASC
