Introducing a simple count subquery to an already existing subquery - sql

Question

I am creating a simple image browser which is connected to an SQLite database. Within the browser, similar images are grouped into an event and each image is labelled with a few tags.
Someone helped me construct this very helpful query below. It contains 5 random tags as an example:
SELECT *
FROM
(SELECT
t.EventId,
SUM(CASE WHEN name = 'necktie' THEN 1 ELSE 0 END) as 'necktie',
SUM(CASE WHEN name = 'shirt' THEN 1 ELSE 0 END) as 'shirt',
SUM(CASE WHEN name = 'suit' THEN 1 ELSE 0 END) as 'suit',
SUM(CASE WHEN name = 'man' THEN 1 ELSE 0 END) as 'man',
SUM(CASE WHEN name = 'male' THEN 1 ELSE 0 END) as 'male'
FROM
TagsMSCV t
WHERE
name IN ('necktie', 'shirt', 'suit', 'man', 'male')
GROUP BY
t.EventId)
ORDER BY
COUNT(*) DESC
This returns how many of each tag (column is called 'name') show up in each event. However now I also need the size of the event (number of unique image id's in the event) which can be accomplished with the below query:
SELECT EventId, COUNT(DISTINCT ImageId)
FROM TagsMSCV
GROUP BY EventId
But I have no idea how to introduce this syntax into the subquery above? If I put it beside t.EventId, it only counts the image id's in event that are tagged with the 5 random tags which is not correct. I need the total unique image id's in the event.

Answer 1

First, your subquery is not necessary. Second, you can use conditional COUNT(DISTINCT):
SELECT t.EventId,
SUM(CASE WHEN name = 'necktie' THEN 1 ELSE 0 END) as necktie,
SUM(CASE WHEN name = 'shirt' THEN 1 ELSE 0 END) as shirt,
SUM(CASE WHEN name = 'suit' THEN 1 ELSE 0 END) as suit,
SUM(CASE WHEN name = 'man' THEN 1 ELSE 0 END) as man,
SUM(CASE WHEN name = 'male' THEN 1 ELSE 0 END) as male
COUNT(DISTINCT CASE WHEN name = 'necktie' THEN imageid END) as necktie_images,
COUNT(DISTINCT CASE WHEN name = 'shirt' THEN imageid END) as shirt_images,
COUNT(DISTINCT CASE WHEN name = 'suit' THEN imageid END) as suit_images,
COUNT(DISTINCT CASE WHEN name = 'man' THEN imageid END) as man_images,
COUNT(DISTINCT CASE WHEN name = 'male' THEN imageid END) as male_images
FROM TagsMSCV t
WHERE name IN ('necktie', 'shirt', 'suit', 'man', 'male')
GROUP BY t.EventId
EDIT:
If you want the total distinct images for an event, then no conditional logic is needed. Just use:
COUNT(DISTINCT imageid) as total_images,
And remove the WHERE clause.