Question

I am trying to join 2 tables and filter on a value not being present.

Table_Items: item_id, title, etc

Table_History: item_id, history_id, action, date

For each disc there are many possible actions (purchased,added,played,ripped,etc) each action creates a new row in table_history linked by item_id. The query I am looking for will return all discs which have not been ripped. My query returns too many rows, everything is returned because there is at least one entry in the history table for each item.

SELECT items.item_id, items.title AS Title, items.`author/creator`, history.action 
FROM items
LEFT JOIN history ON items.item_id = history.item_id
WHERE history.action NOT LIKE 'Ripped%' GROUP BY items.item_id ORDER BY title

I am using mySQL. Help would be appreciated! Thank you.

Answer 1

Just add the action filter to the join and then test for null (anti-join) in the where

SELECT items.item_id, 
       items.title AS title, 
       items.`author/creator`, 
       history.ACTION 
FROM   items 
       LEFT JOIN history 
         ON items.item_id = history.item_id 
            AND history.ACTION LIKE 'Ripped%' 
WHERE  history.item_id IS NULL 
GROUP  BY items.item_id 
ORDER  BY title 

you could also do a not in

SELECT items.item_id, 
   items.title AS title, 
   items.`author/creator`, 
   history.ACTION 
FROM   items 
       LEFT JOIN history 
         ON items.item_id = history.item_id 
WHERE  history.item_id NOT IN (SELECT history.item_id 
                                      FROM   history 
                                      WHERE  history.ACTION LIKE 'Ripped%') 
GROUP  BY items.item_id 
ORDER  BY title