Multiple queries resulting in minimum number of occurrences - sql

Question

I need to find the smallest number of documents retrieved by any subject based on exp_condition. Exp_condition from the subjects table contains a '1' and a '2' column.
Here are the tables:
subjects table:
+-----------------+--------------+
| Field | Type |
+-----------------+--------------+
| username | varchar(255) |
| user_type | varchar(10) |
| years | int |
| low_grade | int |
| high_grade | int |
| on_line | varchar(10) |
| on_line_sources | varchar(255) |
| location | varchar(5) |
| exp_condition | int |
+-----------------+--------------+
tasks table:
+------------+--------------+
| Field | Type |
+------------+--------------+
| username | varchar(255) |
| task | varchar(5) |
| confidence | int |
| sim_helpd | int |
+------------+--------------+
docs table:
+--------------+--------------+
| Field | Type |
+--------------+--------------+
| username | varchar(255) |
| task | varchar(5) |
| doc_type | varchar(10) |
| used_tool | int |
| relevant | int |
| motivational | int |
| concepts | int |
| background | int |
| grade_level | int |
| hands_on | int |
| attachments | int |
+--------------+--------------+
I'm able to generate the number of subjects and number of documents for both exp_condition values. I'm allowed to use multiple queries, but I'm not sure how.
Code for generating number of subjects for exp_condition 1 and 2:
select count(distinct(t2.username))
from tasks as t1
inner join subjects as t2
on t1.username = t2.username group by exp_condition;
Code for generating number of documents for exp_condition 1 and 2:
select count(*), exp_condition
from docs as t1
left join subjects as t2
on t1.username = t2.username
group by exp_condition;
Expected output: two separate numbers for smallest number of documents retrieved by any subject based on exp_condition.
Thanks in advance.

Answer 1

You can use a subquery or a CTE
SubQuery
SELECT exp_condition, MIN(A) as Tasks, MIN(B) as Docs FROM (
SELECT exp_condition, COUNT(DISTINCT t2.username) A, COUNT(DISTINCT (t3.username) B
FROM subjects s
LEFT JOIN tasks T2 ON s.username = t2.username
LEFT JOIN docs T3 ON s.username = t3.username
GROUP BY exp_condition
) A
GROUP BY ex_condition
CTE
;WITH CTE AS (
SELECT exp_condition, COUNT(DISTINCT t2.username) A, COUNT(DISTINCT (t3.username) B
FROM subjects s
LEFT JOIN tasks T2 ON s.username = t2.username
LEFT JOIN docs T3 ON s.username = t3.username
GROUP BY exp_condition
)
SELECT exp_condition, MIN(A) as Tasks, MIN(B) as Docs
FROM CTE
GROUP BY ex_condition