I have three tables: users, accounts and scores. Each query is actually giving me the desired results:
-- This will return all user ids with a count of "calculated" scores
SELECT u.id AS user_id, count(1) AS total FROM scores s
INNER JOIN accounts a ON s.account_id = a.id
INNER JOIN user u ON a.user_id = u.id
WHERE s.status = 'CALCULATED'
GROUP BY user_id;
-- This will return all user ids with a count of non-calculated scores
SELECT u.id AS user_id, count(1) AS failures FROM scores s
INNER JOIN accounts a ON s.account_id = a.id
INNER JOIN user u ON a.user_id = u.id
WHERE s.status <> 'CALCULATED'
GROUP BY user_id;
But I would like to return something like this: user id, total, failures...all in one query!
This can be done with conditional aggregation. Conditions in SUM return 1 or 0 depending on the condition being satisfied.
SELECT u.id AS user_id,
SUM(s.status='CALCULATED'),
SUM(s.status<>'CALCULATED') AS total
FROM scores s
INNER JOIN accounts a ON s.account_id = a.id
INNER JOIN user u ON a.user_id = u.id
GROUP BY u.id;
As a note, you can simplify your query, because the user table is (presumably) not needed:
SELECT a.user_id,
SUM(s.status = 'CALCULATED') as num_calc,
SUM(s.status <> 'CALCULATED') AS num_notcalc
FROM scores s INNER JOIN
accounts a
ON s.account_id = a.id
GROUP BY a.user_id;
Your queries are giving the right answer, but you might also need to be careful about NULL values. If that's a concern, use <=> the NULL-safe equality operator:
SELECT a.user_id,
SUM(s.status = 'CALCULATED') as num_calc,
SUM(NOT s.status <=> 'CALCULATED') AS num_notcalc
FROM scores s INNER JOIN
accounts a
ON s.account_id = a.id
GROUP BY a.user_id;
Related
This query is taking forever to finish in MySql 8, doing some research i found out that the "EXISTS" in this code can be extremely slow in some queries.
When i remove the "OR EXISTS" sub-query part, it runs in less than a second.
So i need to substitute the "OR EXISTS" in this query so i can get all the users i need:
SELECT u.name,
u.email,
u.cpf,
u.register,
r.name AS role_name,
s.name AS sector_name,
b.name AS branch_name,
u.status
FROM users u
INNER JOIN roles r ON r.id = u.role_id
INNER JOIN sectors s ON s.id = u.sector_id
INNER JOIN branches b ON b.id = u.branch_id
WHERE u.status = 2 OR EXISTS (
SELECT *
FROM user_recovery ur
WHERE ur.user_id = u.id
AND ur.status_recovery = 1
)
Is there a way to do it without the "OR EXISTS"?
Or can enforce a full scan
try
you can't get rid of the eXISTS clause because it increases the number of returned rows.
Add a INDEX on user status and user_recovery userid,status_recovery and on the on Clause columns.
SELECT u.name,
u.email,
u.cpf,
u.register,
r.name AS role_name,
s.name AS sector_name,
b.name AS branch_name,
u.status
FROM users u
INNER JOIN roles r ON r.id = u.role_id
INNER JOIN sectors s ON s.id = u.sector_id
INNER JOIN branches b ON b.id = u.branch_id
WHERE u.status = 2
UNION
SELECT u.name,
u.email,
u.cpf,
u.register,
r.name AS role_name,
s.name AS sector_name,
b.name AS branch_name,
u.status
FROM users u
INNER JOIN roles r ON r.id = u.role_id
INNER JOIN sectors s ON s.id = u.sector_id
INNER JOIN branches b ON b.id = u.branch_id
WHERE EXISTS (
SELECT 1
FROM user_recovery ur
WHERE ur.user_id = u.id
AND ur.status_recovery = 1
)
"I'll see your UNION; and raise you a derived table."
SELECT u.name,
u.email,
u.cpf,
u.register,
r.name AS role_name,
s.name AS sector_name,
b.name AS branch_name,
u.status
FROM ( SELECT id
FROM users
WHERE status = 2
UNION DISTINCT -- or UNION ALL; see below
SELECT user_id
FROM user_recovery
WHERE status_recovery = 1 -- see new index
) AS u1
JOIN users AS u USING(id) -- self-join to pick up other columns
JOIN roles r ON r.id = u.role_id
JOIN sectors s ON s.id = u.sector_id
JOIN branches b ON b.id = u.branch_id;
Indexes:
user_recovery: INDEX(status_recovery, user_id) -- in this order
users: INDEX(status, id) -- in this order
(I assume `id` is the PRIMARY KEY in each table)
The general rule here is... When you have a bunch of JOINs, but a single table that controls which rows, but that is messy or slow (eg UNION in this case, GROUP BY or LIMIT in other cases),
Optimize finding the ids (user.id aka user_id) is the optimal way.
Then JOIN back to the original table (if needed), plus the other tables.
In doing all that, it became apparent that a new index for user_recovery might be beneficial.
(If UNION ALL won't produce any dups, switch to it for a little more speed.)
I wanna count all the orders a user has and all the complete orders a user has. I came with this but it´s not working
select
count(a.id) as total,
count(b.id) as complete
from
user
join
orders a on user.id = a.user_id
join
orders b on user.id = b.user_id
where
a.id = 1
and
(b.id = 1 and b.complete = 'yes');
Any idea?
you could sum the order with yes and count the distinct id group by user
select user.id, sum(if(a.complete ='yes',1,0)), count(distinct a.id)
from user
INNER join orders a on user.id = a.user_id
group by user.id
I believe you are searching for grouping (MySQL GROUP BY) by the differents users, and then count all the orders related to each user plus the completed ones. For this approach, you will need to:
(1) Join users with they orders.
(2) Use GROUP BY clause on user.id column.
(3) Count all orders related to each user with COUNT()
(4) Sum all orders related to each user having some specific condition with SUM(CASE WHEN <specific_condition> THEN 1 ELSE 0 END).
In summary, a query like next one should work:
SELECT
u.id,
COUNT(o.id) AS total_orders,
SUM(CASE WHEN o.complete = "yes" THEN 1 ELSE 0 END) AS complete_orders
FROM
user AS u
INNER JOIN
orders AS o ON o.user_id = u.id
GROUP BY
u.id
I am trying to write an SQL SELECT statement with a sub query. There is no error returned but I don't get the results I am expecting. The value for r.related is always NULL.
SELECT
l.id,
u.id as user_id,
u.name,
r.related
FROM
list l
INNER JOIN user u ON u.id = l.user_id
LEFT JOIN (
SELECT COUNT(u.id) AS related, b.group_id
FROM user u
INNER JOIN booking b ON b.user_id = u.id
WHERE u.id != l.user_id
AND b. = 0) AS r ON r.group_id = l.group_id
WHERE
l.group_id = 22
GROUP BY l.id, u.id
ORDER BY l.id
I am writing the sub query correctly?
Here's the problem:
SELECT COUNT(u.id) AS related, b.group_id
FROM user u
INNER JOIN booking b ON b.user_id = u.id
WHERE u.id != b.user_id
AND b. = 0
Look, you are joining user and booking table on booking.user_id = user.id
and
then you are just discarding those matching rows between these two tables in your where condition WHERE user.id != booking.user_id;
It's more like you are looking the differences between Set A and Set B in A intersection B. So in this case you won't find any (i.e. NULL).
I want to count user_id from courses_taken and quiz_attempts table but my query brings me wrong numbers.
SELECT
u.id,
u.email,
u.user,
u.joined,
MAX(qa.last_attempt_time) as last_attempt_time,
COUNT(qa.user_id) total_quiz,
COUNT(ct.user_id) total_courses
FROM users u
LEFT JOIN courses_taken ct
ON u.id = ct.user_id
LEFT JOIN quiz_attempt qa
ON u.id = qa.user_id AND qa.attempt_mode=1
GROUP BY u.id
ORDER BY total_courses DESC
Table structure
users table
id, email, user, joined
quiz_attempt table
id,user_id, last_attempt_time, attempt_mode etc.
courses_taken table
id,user_id,course_id,taken_on etc.
Here i am trying to get all users with their total number of quiz attempts and total number of courses taken. But my query returns same numbers for both quiz attempts and courses taken.
What you can do is use COUNT DISTINCT on a column which varies uniquely with the value that you are trying to count, i.e.:
...
COUNT(DISTINCT qa.id) total_quiz,
COUNT(DISTINCT ct.course_id) total_courses
...
SqlFiddle here
You should not put distinct on the user_ID column but put it on the id for that table like this:
SELECT u.id, u.email, u.userid, u.joined,
MAX(qa.last_attempt_time) as last_attempt_time,
COUNT(DISTINCT qa.id) as total_quiz,
COUNT(DISTINCT ct.id) as total_courses
FROM users u LEFT JOIN
courses_taken ct
ON u.id = ct.user_id LEFT JOIN
quiz_attempt qa
ON u.id = qa.user_id AND qa.attempt_mode = 1
GROUP BY u.id, u.email, u.userid, u.joined
ORDER BY total_courses DESC;
or if this confuses you, you can use subquery like this:-
SELECT
u.id,
u.email,
u.UserId,
u.joined,
qa.last_attempt_time as last_attempt_time,
qa.total_quizCOUNT,
ct.total_coursesCOUNT
FROM users u
LEFT JOIN
(Select user_id, Count(user_id) as total_coursesCOUNT from courses_taken group by user_id) ct
ON u.id = ct.user_id
LEFT JOIN (Select user_id, Count(user_id) total_quizCOUNT, MAX(last_attempt_time) as last_attempt_time from quiz_attempt where attempt_mode = 1 group by user_id) qa
ON u.id = qa.user_id
ORDER BY total_coursesCOUNT DESC
You probably have a cartesian product problem because of the join. The better solution is to pre-aggregate the results. However, in many cases if the tables are not too big, then count(distinct) solves the problem:
SELECT u.id, u.email, u.user, u.joined,
MAX(qa.last_attempt_time) as last_attempt_time,
COUNT(DISTINCT qa.id) as total_quiz,
COUNT(DISTINCT ct.id) as total_courses
FROM users u LEFT JOIN
courses_taken ct
ON u.id = ct.user_id LEFT JOIN
quiz_attempt qa
ON u.id = qa.user_id AND qa.attempt_mode = 1
GROUP BY u.id
ORDER BY total_courses DESC;
Note that this works because you are using MAX() and COUNT(). It would not work with SUM() or AVG().
My query is
select COUNT(*) from result
where test_id in (select test_id
from test_schedule
where scheduler_id in (select user_id
from users
where user_type=1))
Try this:
SELECT COUNT(r.*)
FROM result r
INNER JOIN test_schedule s ON r.test_id = s.test_id
INNER JOIN users u ON s.scheduler_id = u.user_id
WHERE u.user_type = 1
SELECT COUNT(*)
FROM result r
JOIN (SELECT DISTINCT test_id
FROM test_schedule s
JOIN users u ON s.scheduler_id = u.user_id
WHERE u.user_type = 1) s
USING (test_id)
The DISTINCT is necessary to keep rows from being multiplied by all the rows in the other tables that match.
SELECT COUNT(r.*)
FROM result r
RIGHT JOIN test_schedule s USING(test_id)
RIGHT JOIN users u ON s.scheduler_id = u.user_id
WHERE u.user_type = 1