There are two tables
users
+--+----+
|id|name|
+--+----+
1 A
2 B
orders
+--+--------+-------+-------+
|id|subtotal|created|user_id|
+--+--------+-------+-------+
1 10 1000001 1
2 20 1000002 1
3 10 1000003 2
4 10 1000005 1
The idea is to get AVG, SUM and the last created order from the users.
SELECT
users.name,
users.phone,
SUM(a.subtotal),
COALESCE(a.created, NULL)
FROM users
LEFT JOIN
(
SELECT
orders.id,
orders.subtotal,
orders.user_id,
orders.created
FROM
orders
JOIN(
SELECT MAX(i.created) created, i.user_id
FROM orders i
GROUP BY i.user_id
)AS j ON(j.user_id = orders.user_id AND orders.created = j.created) GROUP BY orders.user_id
) AS a ON users.id = a.user_id
GROUP BY users.id
For example the SQL request should return this:
+--+----+---+--------+
|id|name|sum|date |
+--+----+---+--------+
1 A 40 1000005
2 B 10 1000003
But the SQL above failed to calculate sum. What did i miss?
Your query seems way too complicated. How about this?
SELECT u.id, u.name, SUM(o.subtotal), MAX(o.created)
FROM users u LEFT JOIN
orders o
ON u.id = o.user_id
GROUP BY u.id, u.name;
In MySQL it is particularly important to avoid unnecessary subqueries in the FROM clause. These are actually materialized and that can impede the use of indexes for performance.
Related
I have an users table and amount table.
The users table has following columns.
name id
A 1
B 2
C 3
D 4
The amount table has following columns.
userId amount id
1 10 1
1 20 2
1 10 3
2 12 4
I need a sql which sums all the users amount from the amount table
Final output would be
name id totalAmount
A 1 30
B 2 12
C 3 0
D 4 0
I have tried using but does not work. Kindly help
let searchQuery = `SELECT u.id, u.name, (SELECT IFNULL(SUM(amount), 0) from amount WHERE amount.userId = u.id) as totalAmount, FROM users u LEFT JOIN amount amt on u.id = amt.userId WHERE`;
Correct syntax for correlated subquery version
SELECT u.id, u.name, (SELECT coalesce(SUM(a.amount), 0)
FROM amount a
WHERE a.userId = u.id) as totalAmount
FROM users u
You can do it using standard sql aggregation
select
u.name,
u.id,
sum(a.amount) as totalAmount
from users u
left join amount a
on a.userId = u.id
group by u.name, u.id
The left join is just to include those users whitout amounts, which will have a 0 as totalAmount
I have two tables users, orders
each table has below column
users(table)
id
orders(table)
user_id
How can i get the number of users whose order count is 1,2,3,4 ....n?
Like this?
users count | order count
999 | 1
100 | 2
80 | 3
70 | 4
60 | 5
50 | 6
What I have been trying so far is
SELECT cnt.uid as u_cnt, cnt.ocnt as or_cnt
FROM (
SELECT u.id as uid, COUNT(o.id) as o_cnt
FROM users as u
INNER JOIN orders o on u.id = o.user_id
) as cnt;
GROUP BY or_cnt
BUT I get only 1 u_cnt and summed or_cnt
You need two levels of group by clauses here: First, you need to group by user and count the number of orders each user has. Then, you need to take that result, group by the number of orders and count how many users have such an order count.
The easiest way to achieve this is probably with a subquery, where both the inner and outer query have a group by clause:
SELECT cnt.ocnt as or_cnt, COUNT(*) as user_count
FROM (
SELECT u.id as uid, COUNT(o.id) as o_cnt
FROM users as u
INNER JOIN orders o on u.id = o.user_id
GROUP BY u.id -- This was missing in your original query
) as cnt
GROUP BY or_cnt
You can use two levels of aggregation. More importantly, you do not need a JOIN. All the information you need is in orders:
SELECT o_cnt, COUNT(*) as user_count
FROM (SELECT o.user_id, COUNT(*) as o_cnt
FROM orders o
GROUP BY o.user_id
) u
GROUP BY o_cnt
ORDER BY o_cnt;
I want to get the sum of several entities from several tables using a query.
Specifically, I want the devices and messages count of a user. In addition, the timestamp of the last received message for that user.
I have 3 tables:
Users
id name (other fields)
1 Mike ...
2 John ...
3 Yay ...
4 Jim ...
Devices
id user_id (other fields)
1 1 ...
2 1 ...
3 1 ...
4 2 ...
Messages
id device_id message time (other fields)
1 1 Hi 2019-04-07 12:06:44 ...
2 1 Hey 2019-04-06 12:06:44 ...
3 2 Sup 2019-04-05 12:06:44 ...
4 3 Ok 2019-04-04 12:06:44 ...
5 4 Yay 2019-04-08 12:06:44 ...
... and, for example, for user Mike I want to end up with:
Result
nDevices nMessages time
3 4 2019-04-07 12:06:44
Any ideas?
Thanks in advance.
Join the 3 tables and count distinct values of the columns:
select
count(distinct d.id) devicescounter,
count(distinct m.id) messagescounter,
max(m.time) lastmessagetime
from users u
left join devices d on u.id = d.user_id
left join nessages m on m.device_id = d.id
where u.name = 'Mike'
If you want the results for all users:
select
u.id, u.name,
count(distinct d.id) devicescounter,
count(distinct m.id) messagescounter,
max(m.time) lastmessagetime
from users u
left join devices d on u.id = d.user_id
left join nessages m on m.device_id = d.id
group by u.id, u.name
The easiest way to do this would be to get the number of messages and most recent message time for each device in a subquery.
SELECT u.id,
COUNT(d.id) AS num_devices,
SUM(messages) AS num_messages,
MAX(most_recent) AS most_recent_message
FROM users u
JOIN devices d ON d.user_id = u.id
JOIN (SELECT device_id,
COUNT() AS messages,
MAX(TIME) AS most_recent_message
FROM messages
GROUP BY device_id) m ON m.device_id = d.id
GROUP BY u.id
You could try using a join between user and device and a inner join with the subquery for message and device
select a.name, a.id, count(d.user_id), t.nDevice, t.max_time
from Users a
inner join device d on a.id = d.user_id
inner join (
select m.device_id, count(m.device_id) nDevice, max(m.time) max_time
from Messages m
group by m.device_id
) t on t.device_id = d.id
group by a.name, a.id
Take the following data:
db.users
id name
1 David
2 James
3 Mary
db.payments
amount user_id paid
5 1 0
55 1 1
94 1 1
5 2 0
55 2 1
94 2 1
5 2 0
55 2 1
94 2 1
I'd like to LEFT JOIN the payments table to the users table and SUM() the amount where paid = 0:
SELECT users.*, SUM(payments.amount)
FROM users
LEFT JOIN payments
ON users.id = payments.user_id
WHERE payments.paid = 0
GROUP BY users.id
ORDER BY users.id DESC
The problem arises in that 'mary' (user 3) doesn't get returned because she doesn't have any records in the payments table. This is down to the WHERE clause checking for paid = 0.
I'd like it to return 0 as the sum if no records.
Any ideas how to do that?
Move predicate payments.paid = 0 from WHERE to ON clause, like:
SELECT users.*, SUM(payments.amount)
FROM users
LEFT JOIN payments
ON users.id = payments.user_id AND payments.paid = 0
GROUP BY users.id
ORDER BY users.id DESC
If you place the predicate in the WHERE clause LEFT JOIN becomes an INNER JOIN.
You have to put-> sum(isnull(payment.amount,0)) as Payment count in your query
SELECT users.*, SUM(isnull(payments.amount,0))
FROM users
LEFT JOIN payments
ON users.id = payments.user_id
WHERE payments.paid = 0
GROUP BY users.id
ORDER BY users.id DESC
Try this:-
SELECT users.Id, users.name, SUM(case when paid=0 then amount else 0 end) as
req_amt
FROM users
LEFT JOIN payments
ON users.id = payments.user_id
GROUP BY users.id,users.name
ORDER BY users.id DESC
Thanks:-)
It must be pretty easy, but i can't think of any solution nor can I find an answer somewhere...
I got the table 'users'
and one table 'blogs' (user_id, blogpost)
and one table 'messages' (user_id, message)
I'd like to have the following result:
User | count(blogs) | count(messages)
Jim | 0 | 3
Tom | 2 | 3
Tim | 0 | 1
Foo | 2 | 0
So what I did is:
SELECT u.id, count(b.id), count(m.id) FROM `users` u
LEFT JOIN blogs b ON b.user_id = u.id
LEFT JOIN messages m ON m.user_id = u.id
GROUP BY u.id
It obviously doesn't work, because the second left join relates to blogs not users. Any suggestions?
First, if you only want the count value, you could do subselects:
select u.id, u.name,
(select count(b.id) from blogs where userid = u.id) as 'blogs',
(select count(m.id) from messages where userid = u.id) as 'messages'
from 'users'
Note that this is just a plain sql example, I have no mysql db here to test it right now.
On the other hand, you could do a join, but you should use an outer join to include users without blogs but with messages. That would imply that you get several users multiple times, so a group by would be helpful.
If you use an aggregate function in a select, SQL will collapse all your rows into a single row.
In order to get more than 1 row out you must use a group by clause.
Then SQL will generate totals per user.
Fastest option
SELECT
u.id
, (SELECT(COUNT(*) FROM blogs b WHERE b.user_id = u.id) as blogcount
, (SELECT(COUNT(*) FROM messages m WHERE m.user_id = u.id) as messagecount
FROM users u
Why you code does not work
SELECT u.id, count(b.id), count(m.id)
FROM users u
LEFT JOIN blogs b ON b.user_id = u.id <<-- 3 matches multiplies # of rows *3
LEFT JOIN messages m ON m.user_id = u.id <<-- 5 matches multiplies # of rows *5
GROUP BY u.id
The count will be off, because you are counting duplicate items.
Simple fix, but will be slower than option 1
If you only count distinct id's, you will get the correct counts:
SELECT u.id, count(DISTNICT b.id), count(DISTINCT m.id)
FROM users u
LEFT JOIN blogs b ON b.user_id = u.id
LEFT JOIN messages m ON m.user_id = u.id
GROUP BY u.id