maybe it´s easy but i have no clue how to handle this correctly. I have the following table t1 with this data:
-----------------
| id | gr_id |
-----------------
| 1 | a |
| 2 | a |
| 3 | b |
| 4 | b |
| 5 | c |
| 6 | c |
| 7 | d |
| 8 | d |
-----------------
I would like to get randomly gr_ids like this:
-----------------
| id | gr_id |
-----------------
| 3 | b |
| 4 | b |
| 5 | c |
| 6 | c |
| 7 | d |
| 8 | d |
| 1 | a |
| 2 | a |
-----------------
Getting ordered gr_ids ascend and descend is pretty easy, but getting randomly grouped results, is pretty more complicated than i thought it is.
I do not get it, when i use GROUP BY or sth. similar i get for sure only one row each group. How can i randomly order groups, what is the trick here???
Thank you guys for bringing light into darkness ;)
E.g.:
SELECT x.*
FROM my_table x
JOIN
( SELECT DISTINCT gr_id
, RAND() rnd
FROM my_table
) y
ON y.gr_id = x.gr_id
ORDER
BY y.rnd
, x.id;
ORDER BY RAND() should work for you.
Related
I have some table like this
table request_buys
| id | invoice | user_id |
| -- | ----------------- | ------- |
| 3 | 20220405/01104298 | 1 |
table traces
| id | request_buy_id | status_id | created_at |
| -- | -------------- | --------- | ------------------- |
| 37 | 3 | 1 | 2022-03-27 14:12:25 |
| 38 | 3 | 2 | 2022-03-28 14:12:25 |
| 39 | 3 | 3 | 2022-03-29 14:12:25 |
| 40 | 3 | 4 | 2022-03-30 14:12:25 |
| 41 | 3 | 5 | 2022-03-31 14:12:25 |
| 42 | 3 | 6 | 2022-04-01 14:12:25 |
table statuses
| id | nama |
| -- | ----------------- |
| 1 | Order Placed |
| 2 | Order Paid |
| 3 | Accepted |
| 4 | Picked by Courier |
| 5 | In Transit |
| 6 | Delivered |
| 7 | Rated |
| 8 | Rejected |
| 9 | Canceled |
and then i try to design query like below
select
request_buys.invoice,
MAX(traces.id) as traces_id,
MAX(statuses.nama) as statuses_nama
from
`request_buys`
inner join `traces` on `request_buys`.`id` = `traces`.`request_buy_id`
inner join `statuses` on `traces`.`status_id` = `statuses`.`id`
where
`user_id` = 1
group by
request_buys.id
and produces output like the following
output
| invoice | traces_id | statuses_nama |
| ----------------- | --------- | ----------------- |
| 20220405/01104298 | 42 | Picked by Courier |
and the output i expect should be like in the table below
expect
| invoice | traces_id | statuses_nama |
| ----------------- | --------- | ----------------- |
| 20220405/01104298 | 42 | Delivered |
I understand my error is in MAX(statuses.nama) which I should change like removing MAX() in statuses.nama
But i just get error like this "SELECT list is not in GROUP BY clause and contains nonaggregated ... this is incompatible with sql_mode=only_full_group_by"
then I tried some to clear the value "ONLY_FULL_GROUP_BY" with a query like the following
SET sql_mode=(SELECT REPLACE(##sql_mode,'ONLY_FULL_GROUP_BY',''))
and the result is like this
output
| invoice | traces_id | statuses_nama |
| ----------------- | --------- | ----------------- |
| 20220405/01104298 | 42 | Order Placed |
and I'm really stuck at this
and how to make trace_id.status_id from the "GROUP BY" result based on request_buys.id still have a relationship with statuses.id
Your problem lies with your misuse of the MAX(statuses.nama) expression. Based on your expected output,you intend to get the statuses.nama which matches the MAX(traces.id), NOT the MAX(statuses.nama) value which returns the highest value in terms of alphabetic order. In this case, the initial letter 'P' > 'D' . I have tweaked your code a bit and tried it on workbench,supposing there are more than one invoice for a particular user.(e.g insert into request_buys values (4,'20230405/01104298',1); insert into traces values (43,4,7,'2022-04-01 14:12:25');) It works as intended.
select invoice, t.id as traces_id, s.nama as statuses_name from request_buys r
join traces t on r.id=t.request_buy_id
join statuses s on t.status_id=s.id
join
(select traces.request_buy_id, MAX(traces.id) as traces_id
from `request_buys`
inner join `traces` on `request_buys`.`id` = `traces`.`request_buy_id`
where
`user_id` = 1
group by
traces.request_buy_id ) join_t
on t.request_buy_id=join_t.request_buy_id and t.id=join_t.traces_id
;
If I'm understanding correctly, you're trying to retrieve the most recent status for each invoice. Using MAX(nama) won't return that result, because it just picks the maximum status name alphabetically.
Assuming you're using MySQL 8.x, use ROW_NUMBER() to sort and rank the statuses for each invoice, by the most recent date first. Then grab the latest one using where rowNum = 1
WITH cte AS (
SELECT rb.id AS request_buy_id
, rb.invoice
, t.id AS traces_id
, s.nama AS statuses_nama
, ROW_NUMBER() OVER(PARTITION BY rb.id ORDER BY t.created_at DESC) AS RowNum
FROM request_buys rb
INNER JOIN traces t ON rb.id = t.request_buy_id
INNER JOIN statuses s ON t.status_id = s.id
WHERE user_id = 1
)
SELECT *
FROM cte
WHERE RowNum = 1
;
Result:
request_buy_id
invoice
traces_id
statuses_nama
RowNum
3
20220405/01104298
42
Delivered
1
db<>fiddle here
so what I am trying to do is having 3 tables (pictures, collections, and bridge) with the following columns:
Collections Table:
| id | name |
------------------
| 1 | coll1 |
| 2 | coll2 |
------------------
Pictures Table: (timestamps are unix timestamps)
| id | name | timestamp |
-------------------------
| 5 | Pic5 | 1 |
| 6 | Pic6 | 19 |
| 7 | Pic7 | 3 |
| 8 | Pic8 | 892 |
| 9 | Pic9 | 4 |
-------------------------
Bridge Table:
| id | collection | picture |
-----------------------------
| 1 | 1 | 5 |
| 2 | 1 | 6 |
| 3 | 1 | 7 |
| 4 | 1 | 8 |
| 5 | 2 | 5 |
| 6 | 2 | 9 |
| 7 | 2 | 7 |
-----------------------------
And the result should look like this:
| collection_name | picture_count | newest_picture |
----------------------------------------------------
| coll1 | 4 | 8 |
| coll2 | 3 | 9 |
----------------------------------------------------
newest_picture should always be the picture with the heighest timestamp in that collection and I also want to sort the result by it. picture_count is obviously the count of picture in that collection.
Can this be done in a single statement with table joins and if yes:
how can I do this the best way?
A simple method uses correlated subqueries:
select c.*,
(select count(*)
from bridge b
where b.collection = c.id
) as pic_count,
(select p.id
from bridge b join
pictures p
on b.picture = b.id
where b.collection = c.id
order by p.timestamp desc
limit 1
) as most_recent_picture
from collections c;
A more common approach would use window functions:
select c.id, c.name, count(bp.collection), bp.most_recent_picture
from collections c left join
(select b.*,
first_value(p.id) over (partition by b.collection order by p.timestamp desc) as most_recent_picture
from bridge b join
pictures p
on b.picture = p.id
) bp
on bp.collection = c.id
group by c.id, c.name, bp.most_recent_picture;
I have a table like this:
MyTable
-------------------------------
| ID | from | to |
-------------------------------
| 1 | U_002 | C_005 |
| 2 | U_015 | C_004 |
| 3 | C_005 | U_011 |
| 4 | U_008 | C_001 |
| 5 | U_007 | C_005 |
| 6 | U_001 | C_005 |
| 7 | C_004 | U_015 |
| 8 | U_002 | C_002 |
| 9 | U_001 | C_009 |
| 10 | U_010 | C_005 |
| 11 | C_005 | U_001 |
| 12 | U_004 | C_003 |
| 13 | U_005 | C_005 |
| 14 | U_010 | C_001 |
| 15 | C_005 | U_001 |
-------------------------------
ID, is the Unique Incremental Key of the table.
The goal is:
By giving a value (for example: C_005, U_001, C_010, etc..) Obtain the first match of this two conditions: ((from == value) || (to == value)) starting from higher ID.
This means, that data can be "duplicate", but I only wants the first result of the group.
For example, C_004 and U_015, have TWO entries (C_004 -> U_015 and U_015 -> C_004). This should return only ONE.
Since we want to start from higher Id, that mean that it would return only 7 | C_004 | U_015.
Let's put an example:
Value = C_005
The expected output is:
15 | C_005 | U_001
13 | U_005 | C_005
10 | U_010 | C_005
5 | U_007 | C_005
3 | C_005 | U_011
1 | U_002 | C_005
The idea, is to get the ""last"" (because we are starting from higher Id) coincidence of TWO values.
As I have said, two values can have multiple coincidences, but I only want to get the "last" one (Higher Id).
use max()
select max(id) id,`from`,`to`
from table_name
group by `from`,`to`
Your data is messed up because you have duplicates and potentially cycles too. Arrggh. You should fix the data.
But you can still do what you want with a recursive CTE:
with recursive cte as (
select id, f, t, 1 as lev, cast(t as char(1000)) as visited
from t
where f in ('C_005') /*, 'U_001', 'C_010') */
union all
select t.id, t.f, t.t, lev + 1, concat_ws(',', cte.visited, t.f)
from cte join
t
on cte.f = t.t
where cte.visited not like concat('%', t.f, '%')
)
select distinct id, f, t
from cte
order by id desc;
Here is a db<>fiddle.
table 1: forum_threads
+-----+------+-------+
| id | title| status|
+-----+------+-------+
| 1 | a | 1 |
| 2 | b | 1 |
| 3 | c | 1 |
| 4 | d | 1 |
| 5 | e | 1 |
| 6 | f | 1 |
+-----+------+-------+
table 2: forum_comments
+-----+----------+--------------------+
| id | thread_id| comment |
+-----+----------+--------------------+
| 1 | 4 | hai |
| 2 | 4 | hello |
| 3 | 2 | welcome |
| 4 | 2 | whats your name |
| 5 | 6 | how are you |
| 6 | 5 | how old are you |
| 7 | 5 | good |
+-----+----------+--------------------+
wanted output
+-----------+----------+-----------------+
| thread_id | title | comment_count |
+-----------+----------+-----------------+
| 5 | e | 2 |
| 6 | f | 1 |
| 2 | b | 2 |
| 4 | d | 2 |
+-----------+----------+-----------------+
my Query
SELECT forum_threads.*,forum_comments.*,count(forum_comments.id) as comment_count
FROM forum_comments
LEFT JOIN forum_threads ON forum_comments.thread_id = forum_threads.id
GROUP BY forum_threads.id
ORDER BY forum_comments.id desc
Here I am trying to get the titles by the latest comment.
when I give ORDER BY forum_comments.id this returns the wrong order.
I need to order by the latest comments in the forum_comments table.
this query returns the wrong order please help me to find out the correct order.
how could I solve this easily?
This query should give you the expected result:
select t2.thread_id, t1.title, t2.comment_count from forum_threads as t1,
(SELECT id, thread_id, count(comment) as comment_count from forum_comments group by thread_id) as t2
where t1.id = t2.thread_id order by t2.id desc;
Instead of using forum_threads.* and forum_comments.* can you give specific column names and try.
If that doesn't work you should try explicitly assigning primary and foreign keys.
I am designing a simple architecture where i have a table which stores users and some elements that they like so my table structure is something like this:
+---------+---------+
| user_id | like_id |
+---------+---------+
| 1 | 4 |
| 2 | 2 |
| 4 | 4 |
| 4 | 3 |
| 5 | 4 |
| 6 | 7 |
| 7 | 5 |
| 34 | 6 |
| 3 | 8 |
| 2 | 3 |
| 2 | 5 |
| 1 | 3 |
| 1 | 10 |
| 1 | 12 |
| 2 | 10 |
+---------+---------+
Now what i will have is id of any user (lets say user_id = 1 ) and i want a query to get all the other users who have similar Likes as that of 1.
So in the Output for user_id = 1 will be :
+---------------------------+------------------------+----------------+
| users_with_common_likes | no_of_common_likes | common_likes |
+---------------------------+------------------------+----------------+
| 4 | 2 | 3,4 |
| 2 | 2 | 3,10 |
| 5 | 1 | 4 |
+---------------------------+------------------------+----------------+
What I have achieved :
I can do this using a sub-query as below :
SELECT user_id
FROM `user_likes`
WHERE `like_id`
IN (
SELECT GROUP_CONCAT( `like_id` )
FROM user_likes
WHERE user_id =1
)
AND user_id !=1
LIMIT 0 , 30
However this query is not giving all the users,it misses the user_id = 2 which has like id 3 in common with user_id=1.
and i cant figure out how to find the remaining 2 columns.
Also I feel that this is not the best way to to this as this table will contain thousands of data and it may effect system performance.
I would like to do this with a single Mysql Query.
This assumes a PK formed on user_id,like_id...
SELECT y.user_id
, GROUP_CONCAT(y.like_id) likes
, COUNT(*) total
FROM my_table x
JOIN my_table y
ON y.like_id = x.like_id
AND y.user_id <> x.user_id
WHERE x.user_id = 1
GROUP
BY y.user_id;