sql query using left joins and where clause

Question

I have the following query

SELECT *
  FROM tbl_events AS event
       LEFT JOIN tbl_business_events AS bevent 
                 ON event.event_id = bevent.event_id 
       LEFT JOIN tbl_business_sector AS bsec 
                 ON event.event_id = bsec.event_id 
       LEFT JOIN tbl_sectors AS sector 
                 ON bsec.sector_id = sector.sector_id 
       LEFT JOIN tbl_event_location AS eloc 
                 ON event.event_id = eloc.event_id 
       LEFT JOIN tbl_locations AS location 
                 ON location.location_id = eloc.location_id 
 WHERE event.event_type = 1

which i use to pull out all the details of my event listings, this works but i now want to pull out the events profile picture from another table tbl_event_images. This table stores all the events images but has a field called is_profile_picture which determins if it is the profile pic or not (value is 0 for not and 1 if the image is the profile pic)

so i tried the following query to grab the event profile picture as well as the rest of the information with the following query

SELECT *
  FROM tbl_events AS event
       LEFT JOIN tbl_event_images AS eIMG 
                 ON event.event_id = eIMG.event_id
       LEFT JOIN tbl_business_events AS bevent 
                 ON event.event_id = bevent.event_id
       LEFT JOIN tbl_business_sector AS bsec 
                 ON event.event_id = bsec.event_id
       LEFT JOIN tbl_sectors AS sector 
                 ON bsec.sector_id = sector.sector_id
       LEFT JOIN tbl_event_location AS eloc 
                 ON event.event_id = eloc.event_id
       LEFT JOIN tbl_locations AS location 
                 ON location.location_id = eloc.location_id
 WHERE event.event_type =1

but this query returns a new row for each photo the event has in that table.

so i then tried to add another where clause to the above AND eIMG.is_profile_picture =1

but because not every listing has photos let alone a profile picture the above query only returns the events that have a profile picture.

how can i return 1 row for each event regardless if they have a profile pic or not? if they do then it will add the name of the image if it doesnt it sets it to NULL

Thanks Luke

Answer 1

Try this

SELECT *
FROM tbl_events AS event
LEFT JOIN tbl_event_images AS eIMG ( ON event.event_id = eIMG.event_id AND  eIMG.is_profile_picture = 1 )
LEFT JOIN tbl_business_events AS bevent ON event.event_id = bevent.event_id
LEFT JOIN tbl_business_sector AS bsec ON event.event_id = bsec.event_id
LEFT JOIN tbl_sectors AS sector ON bsec.sector_id = sector.sector_id
LEFT JOIN tbl_event_location AS eloc ON event.event_id = eloc.event_id
LEFT JOIN tbl_locations AS location ON location.location_id = eloc.location_id
WHERE event.event_type =1

Answer 2

Instead of using WHERE criteria add the is_profile_picture condition to your JOIN criteria:

SELECT *
FROM tbl_events AS event
LEFT JOIN tbl_event_images AS eIMG 
   ON   event.event_id = eIMG.event_id 
    AND eIMG.is_profile_picture =1
LEFT JOIN tbl_business_events AS bevent 
   ON event.event_id = bevent.event_id
LEFT JOIN tbl_business_sector AS bsec 
   ON event.event_id = bsec.event_id
LEFT JOIN tbl_sectors AS sector 
   ON bsec.sector_id = sector.sector_id
LEFT JOIN tbl_event_location AS eloc 
   ON event.event_id = eloc.event_id
LEFT JOIN tbl_locations AS location 
   ON location.location_id = eloc.location_id
WHERE event.event_type =1

WHERE filters all results, and in this case effectively negates your use of LEFT JOIN . Adding to the JOIN criteria itself means only some pictures will join, but all the results of your original query will still be returned.