How to select all enteties grouped by common propertie without loop? - mysql

Is there any way to fatch all entities from table grouped by common property while loop?
Table storage looks like this
id | product_id | category_id
-----------+-----------------------+--------------------------
1 | 1 | 15
2 | 2 | 17
3 | 3 | 18
4 | 4 | 17
5 | 5 | 15
6 | 6 | 17
7 | 7 | 18
and final result supposed to look like this
id | product_id | category_id
-----------+-----------------------+--------------------------
1 | 1 | 15
2 | 2 | 17
3 | 3 | 18
4 | 5 | 15
5 | 4 | 17
6 | 7 | 18
7 | 6 | 15
What i want is this:
Select each record grouped by category id. It means, if table size is 3200, i need to select all of 3200 records grouped by category id in ASC order


You seem to want the values interleaved. You can use row_number() in the order by:
select s.*
from storage s
order by row_number() over (partition by storage_id order by id),
storage_id;
Here is a db<>fiddle.
EDIT:
In older versions of MySQL, you can assign a sequential number within each group using variables and then use that for ordering:
select s.*
from (select s.*,
(#rn := if(#sid = storage_id, #rn + 1,
if(#sid := storage_id, 1, 1)
)
) as seqnum
from (select s.* from storage s order by storage_id, id) s cross join
(select #rn := 0, #sid := -1) params
) s
order by seqnum, id;
The SQL Fiddle has both methods.

Related

How to increment count of occurences of column value in MySQL

I have the following column names:
customer_email
increment_id
other_id (psuedo name)
created_at
increment_id and other_id will be unique, customer_email will have duplicates. As the results are returned I want to know what number of occurance of the email it is.
For each row, I want to know how many times thecustomer_email value has shown up so far. There will be an order by clause at the end for the created_at field and I plan to also add a where clause of where occurrences < 2
I am querying > 5 million rows but performance isn't too important because I'll be running this as a report on a read-replica database from production. In my use case, I will sacrifice performance for robustness.
| customer_email | incremenet_id | other_id | created_at | occurances <- I want this |
|----------------|---------------|----------|---------------------|---------------------------|
| joe#test.com | 1 | 81 | 2019-11-00 00:00:00 | 1 |
| sue#test.com | 2 | 82 | 2019-11-00 00:01:00 | 1 |
| bill#test.com | 3 | 83 | 2019-11-00 00:02:00 | 1 |
| joe#test.com | 4 | 84 | 2019-11-00 00:03:00 | 2 |
| mike#test.com | 5 | 85 | 2019-11-00 00:04:00 | 1 |
| sue#test.com | 6 | 86 | 2019-11-00 00:05:00 | 2 |
| joe#test.com | 7 | 87 | 2019-11-00 00:06:00 | 3 |

You can use variables in earlier versions of MySQL:
select t.*,
(#rn := if(#ce = customer_email, #rn + 1,
if(#ce := customer_email, 1, 1)
)
) as occurrences
from (select t.*
from t
order by customer_email, created_at
) t cross join
(select #ce := '', #rn := 0) params;
In MyQL 8+, I would recommend row_number():
select t.*,
row_number() over (partition by customer_email order by created_at) as occurrences
from t;

If you are running MySQL 8.0, you can just do a window count:
select
t.*,
count(*) over(partition by customer_email order by created_at) occurences
from mytable t
You don't need an order by clause at the end of the query for this to work (but you need one if you want to order the results).
If you need to filter on the results of the window count, an additional level is needed, since window functions cannot be used in the where clause of a query:
select *
from (
select
t.*,
count(*) over(partition by customer_email order by created_at) occurences
from mytable t
) t
where occurences < 2

How can you update a table with an ascending order position based on different groups in MYSQL?

I am struggling with this complex query. I am trying to insert the order position of some products.
For example,
I have currently table 1 with a position of NULL, I want to group each Product ID and assign each size a menu position based on ProductID group and using this FIND_IN_SET:
FIND_IN_SET(size,"UNI,XS,S,M,L,XL,XXL,3XL,4XL,40,41,42,43,44,45,46,47,48,49,50,51,52,53,54,55,56,57,58,59,60") asc;
In other words, I want it to look like Table2.
Table1
ID | ProductID | Size | Menu_position
1 | 100 | S | NULL
2 | 100 | M | NULL
3 | 100 | L | NULL
4 | 101 | 40 | NULL
5 | 101 | 41 | NULL
6 | 101 | 42 | NULL
7 | 102 | XS | NULL
8 | 102 | L | NULL
Table2
ID | ProductID | Size | Menu_position
1 | 100 | S | 1
2 | 100 | M | 2
3 | 100 | L | 3
4 | 101 | 40 | 1
5 | 101 | 41 | 2
6 | 101 | 42 | 3
7 | 102 | XS | 1
8 | 102 | L | 2
What I collected so far:
Number of products Group:select count(distinct ProductID) from Table1
Sort size based on specific order: SELECT * FROM Table1 ORDER BY FIND_IN_SET(size,"UNI,XS,S,M,L,XL,XXL,3XL,4XL,40,41,42,43,44,45,46,47,48,49,50,51,52,53,54,55,56,57,58,59,60") asc;

You can use variables in pre-MySQL 8.0:
SELECT t1.*,
(#rn := if(#p = productid, #rn + 1,
if(#p := productid, 1, 1)
)
) as menu_position
FROM (SELECT t1.*
FROM Table1 t1
ORDER BY ProductId,
FIND_IN_SET(size, 'UNI,XS,S,M,L,XL,XXL,3XL,4XL,40,41,42,43,44,45,46,47,48,49,50,51,52,53,54,55,56,57,58,59,60') asc
) AS alias CROSS JOIN
(SELECT #p := -1, #rn := 0) params;
In MySQL 8+, this is much simpler:
select t1.*,
row_number() over (partition by productid order by FIND_IN_SET(size, 'UNI,XS,S,M,L,XL,XXL,3XL,4XL,40,41,42,43,44,45,46,47,48,49,50,51,52,53,54,55,56,57,58,59,60')) as menu_position
from table1 t1

Create a two-column table containing all the the Size values in one column and the integer order of those sizes in the second column--call that table menu_pos. Join this to your Table on size, to produce a table or view (call this product_pos) containing columns product_id, size, and menu_pos. Then modify the menu_pos values to ensure that they are strictly sequential using a window function, such as:
select
product_id,
size,
rank() over (partition by product_id order by menu_pos) as new_menu_pos
from
product_pos;
Window functions require MySQL 8.

Get 10 latest records per category even some has less then 10

This is example of my table :
+-----+-----+------------+--------+-------------+--------------+
| LID | AID | Created | TypeID | PaymentDate | PaymentValue |
+-----+-----+------------+--------+-------------+--------------+
| 1 | 529 | 2017-05-12 | 1 | 2017-05-12 | 100 |
+-----+-----+------------+--------+-------------+--------------+
| 2 | 529 | 2018-04-10 | 4 | 2018-04-10 | 200 |
+-----+-----+------------+--------+-------------+--------------+
| 3 | 441 | 2014-01-23 | 3 | 2014-01-23 | 300 |
+-----+-----+------------+--------+-------------+--------------+
| 4 | 324 | 2017-09-14 | 1 | 2017-09-14 | 400 |
+-----+-----+------------+--------+-------------+--------------+
| 5 | 111 | 2018-05-12 | 0 | 2018-05-12 | 340 |
+-----+-----+------------+--------+-------------+--------------+
| 6 | 529 | 2018-05-12 | 1 | 2018-05-12 | 100 |
+-----+-----+------------+--------+-------------+--------------+
| 7 | 529 | 2018-06-12 | 1 | 2018-05-12 | 100 |
+-----+-----+------------+--------+-------------+--------------+
| 8 | 529 | 2018-07-12 | 1 | 2018-05-12 | 100 |
+-----+-----+------------+--------+-------------+--------------+
| 9 | 529 | 2018-08-12 | 1 | 2018-05-12 | 100 |
+-----+-----+------------+--------+-------------+--------------+
| 10 | 529 | 2018-09-12 | 1 | 2018-05-12 | 100 |
+-----+-----+------------+--------+-------------+--------------+
| 11 | 529 | 2018-01-12 | 1 | 2018-05-12 | 100 |
+-----+-----+------------+--------+-------------+--------------+
| 12 | 529 | 2018-05-14 | 1 | 2018-05-12 | 100 |
+-----+-----+------------+--------+-------------+--------------+
| 13 | 529 | 2018-05-21 | 1 | 2018-05-12 | 100 |
+-----+-----+------------+--------+-------------+--------------+
| 14 | 529 | 2018-03-12 | 1 | 2018-05-12 | 100 |
+-----+-----+------------+--------+-------------+--------------+
Here another table
+-----+-------+
| ID |caption|
+-----+-------+
| 0 | bad |
+-----+-------+
| 1 | good |
+-----+-------+
I need to get 10 latest records per AID. If there less than 10 records for some AID anyway i need to get ten rows and put "No payment date" into PaymentDate and Created fields, Null into TypeID and 0 into PaymentValue. I can get 10 or less latest records with
select *
from (select *,
(#rn := if(#c = AID, #rn + 1,
if(#c := AID, 1, 1)
)
) as rn
from history cross join
(select #rn := 0, #c := -1) params
order by AID, Created desc
) t
having rn <= 10;
But i dont know how force mysql to output 10 rows for each AID. Help me please.
Result should be in a form
AID,TypeId,Created,Caption

I have done it.
This query needs to create a row of 10 records to combine with distinct AID valies in the table. I was able to show the result for Amount and Create date and will leave it to you to continue since you will get the idea.
The critical part is to build a table with 10 rows times distinct AID so about 40 rows in table r. Then do a left join to table t which is similar to what you have done. Table t gets a rank of at most 10 records. Any missing rank up to 10 recs will be filled by table r. Coalesce will assign the default values such as 0 fro amount and 'no create date' for date.
http://sqlfiddle.com/#!9/855c21/2
SELECT coalesce(r.aid, t.aid) as aid,
coalesce(t.paymentvalue, 0) as paymentvalue,
coalesce(cast(t.created as char), 'no create date') as created
FROM (select * from (
select 1 as rw union
select 2 union select 3
union select 4 union select 5
union select 6 union select 7
union select 8 union select 9
union select 10) u
cross join (select distinct aid
from history) h
) as r
LEFT JOIN (
SELECT a.aid, a.paymentvalue,
a.created, count(*) rn
FROM history a
JOIN history b
ON a.aid = b.aid
AND a.created <= b.created
GROUP BY a.aid, a.created
HAVING COUNT(*) <= 10) t
on r.rw=t.rn and r.aid=t.aid
order by aid, created;

I have added RIGHT JOIN to bring in the null rows to top up to 10 (or n) rows per AID. Initially I use SELECT 1 UNION SELECT 2 ... to generate the 10 rows. In order to make it easier to increase the number of rows (say 100), I am trying this idea of generate_series equivalent for mysql. In order for this to work, the number of rows in history table must be equal to greater than the number of rows required per AID.
select t1.lid
,t2.aid
,coalesce(t1.created, "no created date") as created
,t1.typeID
,coalesce(t1.paymentdate, "no payment date") as paymentDate
,coalesce(t1.paymentvalue, 0) as paymentValue
,t2.rn
from
(
select *,
(#rn := if(#c = AID, #rn + 1,
if(#c := AID, 1, 1)
)
) as rn
from history cross join
(select #rn := 0, #c := -1) params
order by AID, Created desc
) t1
right join
( select *
from (select distinct aid from history ) h1
cross join
(select rn -- generate table with n rows numbered from 1 to n
from
(select
#num:= 0) init
cross join
(select #num := #num +1 rn
from history ) t -- assume history has at least 10 rows
limit
10 ) h2 -- n = 10; change it to the number of rows per aid required
) t2
on t1.aid = t2.aid and t1.rn = t2.rn
order by t2.aid, t2.rn

Rank users in mysql by their total points across multiple rows

I have very much similar kind of requirement as described in this question.
Rank users in mysql by their points
The only difference is in my data. The above problem has the data where table has only row per student. But in my case there may be a possibility that table contains multiple rows for a single student like this
Student 1 points 80
Student 2 points 77.5
Student 2 points 4.5
Student 3 points 77
Student 4 points 77
So now rank should be calculated based on the SUM of points (total) that user has. So in this case result would be.
Student 2 Rank 1 with 82 points
Student 1 Rank 2 with 80 points
Student 3 Rank 3 with 77 points
Student 4 Rank 3 with 77 points
SQL Fiddle for data
I tried couple of things with the solution of above question but couldn't get the result. Any help would be appreciated.

Using the same query in my previous answer just change the table student for a subquery to combine all records of every student
change [student er] for
(SELECT `id`, SUM(`points`) as `points`
FROM students
GROUP BY `id`) er
SQL DEMO
select er.*,
(#rank := if(#points = points,
#rank,
if(#points := points,
#rank + 1,
#rank + 1
)
)
) as ranking
from (SELECT `id`, SUM(`points`) as `points`
FROM students
GROUP BY `id`) er cross join
(select #rank := 0, #points := -1) params
order by points desc;
OUTPUT
| id | points | ranking |
|----|--------|---------|
| 5 | 91 | 1 |
| 6 | 81 | 2 |
| 1 | 80 | 3 |
| 2 | 78 | 4 |
| 3 | 78 | 4 |
| 4 | 77 | 5 |
| 7 | 66 | 6 |
| 8 | 15 | 7 |

Try this:
select id, points, #row := ifnull(#row, 0) + diff rank
from (select *, ifnull(#prev, 0) != points diff, #prev := points
from (select id, sum(points) points
from students
group by 1
order by 2 desc) x) y
See SQLFiddle

EDITED:
(This should work)
SELECT I.Id, I.Points, Rk.Rank
FROM
(SELECT Id, Points, #Rk := #Rk+1 As Rank
FROM (SELECT id, SUM(points) AS Points
FROM students
GROUP BY id
ORDER BY Points DESC) As T,
(SELECT #Rk := 0) AS Rk) As I
INNER JOIN
(SELECT *
FROM (
SELECT Id, Points, #Rk2 := #Rk2+1 As Rank
FROM (SELECT id, SUM(points) AS Points
FROM students
GROUP BY id
ORDER BY Points DESC) As T1,
(SELECT #Rk2 := 0) AS Rk) AS T2
GROUP BY Points) As Rk
USING(Points)
The output will be:
| Id | Points | Rank |
|----|--------|---------|
| 5 | 91 | 1 |
| 6 | 81 | 2 |
| 1 | 80 | 3 |
| 2 | 78 | 4 |
| 3 | 78 | 4 |
| 4 | 77 | 6 |
| 7 | 66 | 7 |
| 8 | 15 | 8 |
After two Ids in 4th position you'll get the 6th position because 5 Ids are before of the 6th.

Get the top n results per group [duplicate]

This question already has answers here:
Get top n records for each group of grouped results
(12 answers)
Using LIMIT within GROUP BY to get N results per group?
(14 answers)
Closed 5 years ago.
I am using the sql to retrieve the last 20 rows from the table grouped by date. I would like to limit it so that within each post_day group only the top 10 rows votes DESC are selected.
SELECT *, DATE(timestamp) as post_day
FROM stories
ORDER BY post_day DESC, votes DESC
LIMIT 0, 20
This is what the table looks like:
STORYID TIMESTAMP VOTES
1 2015-03-10 1
2 2015-03-10 2
3 2015-03-9 5
4 2015-03-9 3

Schema
create table stories
( storyid int auto_increment primary key,
theDate date not null,
votes int not null
);
insert stories(theDate,votes) values
('2015-03-10',1),
('2015-03-10',2),
('2015-03-09',5),
('2015-03-09',3),
('2015-03-10',51),
('2015-03-10',26),
('2015-03-09',75),
('2015-03-09',2),
('2015-03-10',12),
('2015-03-10',32),
('2015-03-09',51),
('2015-03-09',63),
('2015-03-10',1),
('2015-03-10',11),
('2015-03-09',5),
('2015-03-09',21),
('2015-03-10',1),
('2015-03-10',2),
('2015-03-09',5),
('2015-03-09',3),
('2015-03-10',51),
('2015-03-10',26),
('2015-03-09',75),
('2015-03-09',2),
('2015-03-10',12),
('2015-03-10',44),
('2015-03-09',11),
('2015-03-09',7),
('2015-03-10',19),
('2015-03-10',7),
('2015-03-09',51),
('2015-03-09',79);
The Query
set #rn := 0, #thedate := '';
select theDate, votes
from
(
select storyid, theDate, votes,
#rn := if(#thedate = theDate, #rn + 1, 1) as rownum,
#thedate := theDate as not_used
from stories
order by theDate, votes desc
) A
where A.rownum <= 10;
The Results
+------------+-------+
| theDate | votes |
+------------+-------+
| 2015-03-09 | 79 |
| 2015-03-09 | 75 |
| 2015-03-09 | 75 |
| 2015-03-09 | 63 |
| 2015-03-09 | 51 |
| 2015-03-09 | 51 |
| 2015-03-09 | 21 |
| 2015-03-09 | 11 |
| 2015-03-09 | 7 |
| 2015-03-09 | 5 |
| 2015-03-10 | 51 |
| 2015-03-10 | 51 |
| 2015-03-10 | 44 |
| 2015-03-10 | 32 |
| 2015-03-10 | 26 |
| 2015-03-10 | 26 |
| 2015-03-10 | 19 |
| 2015-03-10 | 12 |
| 2015-03-10 | 12 |
| 2015-03-10 | 11 |
+------------+-------+
20 rows in set, 1 warning (0.00 sec)

Usually you should use ROW_NUMBER() per group to order records inside of each group and then select records with ROW_NUMBER <= 10. In MySQL there is no ROW_NUMBER() aggregate function but you can use User-Defined variables in MySQL to emulate ROW_NUMBER()
select storyId, post_day , votes
from (
select storyId,
DATE(timestamp) as post_day,
votes,
#num := if(#grp = DATE(timestamp), #num + 1, 1) as row_number,
#grp := DATE(timestamp) as dummy
from stories,(select #num := 0, #grp := null) as T
order by DATE(timestamp) DESC, votes DESC
) as x where x.row_number <= 10;
SQLFiddle demo
Also look at:
How to select the first/least/max row per group in SQL