I have the following two tables. I need to select all the lightboxes from lightboxes_tbl where author ='scott@co.com'. That's obviously the easy part. Where I am stuck is that I also want to select in the same query the number of assets in each lightbox. For example, 'aircraft-types' lightbox (id = 100 / lightbox_id = 100) would return 2 assets. The 'maintenance' lightbox (id = 101 / lightbox_id = 101) would return 1 asset.
Thanks!
lightboxes_tbl
+-----+----------------+---------------+---------------------+
|id |lightbox_name |author |authoried_viewers |
+-----+----------------+---------------+---------------------+
|100 | aircraft-types |scott@co.com |jon@co.com,aj@co.com |
+-----+----------------+---------------+---------------------+
|101 | maintenance |scott@co.com |nicole@co.com |
+-----+----------------+---------------+---------------------+
lightbox_assets_tbl
+-----+-------------+-------------+---------------+----------+
|id |lightbox_id |asset_name |asset_path | asset_id |
+-----+-------------+-------------+---------------+----------+
|1 |100 |a321.jpg |project1/imgs/ | 3700 |
+-----+-------------+-------------+---------------+----------+
|2 |100 |b757.jpg |project1/imgs/ | 3444 |
+-----+-------------+-------------+---------------+----------+
|3 |101 |engine.jpg |project4/imgs/ | 1444 |
+-----+-------------+-------------+---------------+----------+
Make use of LEFT JOIN
and COUNT()
SELECT l.*, COUNT(a.lightbox_id) total_assets
FROM lightboxes_tbl l LEFT JOIN lightbox_assets_tbl a
ON l.id = a.lightbox_id
WHERE l.author = 'scott@co.com'
GROUP BY l.id
Output:
| ID | LIGHTBOX_NAME | AUTHOR | AUTHORIED_VIEWERS | TOTAL_ASSETS | |-----|----------------|--------------|----------------------|--------------| | 100 | aircraft-types | scott@co.com | jon@co.com,aj@co.com | 2 | | 101 | maintenance | scott@co.com | nicole@co.com | 1 |
Here is a SQLFiddle demo
Recommended reading:
Join to the assts table:
select
lb.id, lb.lightbox_name, lb.author, lb.authoried_viewers,
sum(a.id is not null) asset_count
from lightboxes_tbl
left join lightbox_asset_tbl a
on a.lightbox_id = lb.id
where author ='scott@co.com'
group by lb.id, lb.lightbox_name, lb.author, lb.authoried_viewers
There's a little trick in there: sum()
is used to count how many rows are not null in the asst table, which will produce a total of zero for light boxes that have no assets - something that count()
won't do when using a left join.
BTW, in mysql a boolean result is 1 if true, 0 if false, so summing a condition neatly counts how many times it was true.
You probably want something along the lines of this query...
SELECT LBT.id, LBT.lightbox_name, LBT.author, LBTA.id, LBTA.asset_name, LBTA.asset_path, LBTA.asset_id FROM lightboxes_tbl LBT JOIN lightbox_assets_tbl LBTA ON LBTA.lightbox_id = LBT.id WHERE author = 'scott@co.com'
azsl1326
this I write simple query for example, hope it helps,
select
a.id, a.lightbox_name, b.id, b.lightbox_id, b.asset_name, b.asset_id
from lightboxes_tbl a
join lightbox_assets_tbl b
on (a.id = b.lightbox_id)
where a.author = "scott@co.com"
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