MySQL - loop through rows - mysql

Question

I have the following code
select count(*)
from (select Annotations.user_id
from Annotations, Users
where Users.gender = 'Female'
and Users.user_id = Annotations.user_id
and image_id = 1
group by Annotations.user_id
having sum(case when stem = 'taxi' then 1 else 0 end) > 0 and
sum(case when stem = 'zebra crossing' then 1 else 0 end) > 0
) Annotations
It produces a count of how many females who have given the stem 'taxi' and 'zebra crossing' for image 1.
Sample data
user id, image id, stem
1 1 image
1 1 taxi
1 1 zebra crossing
2 1 person
2 1 zebra crossing
2 1 taxi
3 1 person
3 1 zebra crossing
Expected result (or similar)
stem1, stem2, count
taxi , zebra crossing 2
person, zebra crossing 2
However, as there are over 2000 stems, I cannot specify them all.
How would I go around looping through the stem rows with the image_id = 1 and gender = female as opposed to specifying the stem string?
Thank you

Answer 1

As per my understanding, you need to fetch female users that have 2 or more stems
Update: It seems you need to display the user's that have a stem that is used by another user too, I have updated the query for the same
SELECT
distinct a.user_id,
group_concat(DISTINCT a.stem ORDER BY a.stem)
FROM
Annotations a
JOIN Users u ON ( a.user_id = u.user_id AND u.gender = 'Female' )
JOIN
(
SELECT
b.user_id,
b.stem
FROM
Annotations b
) AS b ON ( a.user_id <> b.user_id AND b.stem = a.stem )
WHERE
a.image_id = 1
GROUP BY
a.user_id

Answer 2

UPDATE: As I understand it, you want to select all combinations of 2 stems, and get a count of how many users have that combination of stems. Here is my solution:
SELECT stem1, stem2, count(*) as count FROM
(
SELECT a.user_id,a.image_id,a.stem as stem1,b.stem as stem2
FROM Annotations a JOIN Annotations b
ON a.user_id=b.user_id && b.image_id=a.image_id && a.stem!=b.stem
JOIN Users ON Users.user_id = a.user_id
WHERE Users.gender = "Female"
) as stems GROUP BY stem1, stem2 having count > 1 WHERE image_id=1;
The caveat here is that it will return 2 rows for each combinations of stems. (The second occurrence will have the stems in reverse order).

Answer 3

Here's my attempt to solve your problem:
SELECT COUNT(*) AS Count, a1.stem AS Stem1, a2.Stem AS Stem2
FROM Annotations AS a1
INNER JOIN Annotations AS a2 ON a1.user_id = a2.user_id AND a1.image_id = a2.image_id
AND a1.stem < a2.stem
WHERE a1.image_id = 1
GROUP BY a1.stem, a2.Stem
HAVING COUNT(*) > 1;
I did not include image_id logic.
Please see my SQL Fiddle here: http://sqlfiddle.com/#!2/4ee69/33
Based on the following data (copied from yours) I get the result posted underneath it.
CREATE TABLE Annotations
(`user_id` int, `image_id` int, `stem` varchar(14))
;
INSERT INTO Annotations
(`user_id`, `image_id`, `stem`)
VALUES
(1, 1, 'image'),
(1, 1, 'taxi'),
(1, 1, 'zebra crossing'),
(2, 1, 'person'),
(2, 1, 'zebra crossing'),
(2, 1, 'taxi'),
(3, 1, 'person'),
(3, 1, 'zebra crossing')
;
COUNT STEM1 STEM2
2 person zebra crossing
2 taxi zebra crossing