I have mysql table called ware_stock_transaction and it has order_no, order_type, created_date, item_no.
I want to get the last 10 record from each item, like this:
item A (10 records)
item B (10 records)
item C (10 records)
In MySQL, you can use variables:
select wst.*
from (select wst.*,
(#rn := if(#i = item_no, #rn + 1,
if(#i := item_no, 1, 1)
)
) as rn
from ware_stock_transaction wst cross join
(select #rn := 0, #i := '') params
order by item_no, created_date desc
) wst
where rn <= 10;
Related
Need to find median value of time difference between sent date and click date (in seconds) for each type of emails. I found solution just for all data:
SET #rowindex := -1;
SELECT g.type, g.time_diff
FROM
(SELECT #rowindex:=#rowindex + 1 AS rowindex,
TIMESTAMPDIFF(SECOND, emails_sent.date_sent, emails_clicks.date_click) AS time_diff,
emails_sent.id_type AS type
FROM emails_sent inner join emails_clicks on emails_sent.id = emails_clicks.id_email
ORDER BY time_diff) AS g
WHERE g.rowindex IN (FLOOR(#rowindex / 2) , CEIL(#rowindex / 2));
Is it possible to add group by id_type statement?
Thanks!
First, you need to enumerate the rows for each type. Using variables, this code looks like:
select sc.*,
(#rn := if(#t = id_type, #rn + 1,
if(#t := id_type, 1, 1)
)
) as seqnum
from (select timestampdiff(second, s.date_sent, c.date_click) as time_diff,
s.id_type,
from emails_sent s inner join
emails_clicks c
on s.id = c.id_email
order by time_diff
) sc cross join
(select #t := -1, #rn := 0) as params;
Then, you need to bring in the total number for each type and do the calculation for the median:
select sc.id_type, avg(time_diff)
from (select sc.*,
(#rn := if(#t = id_type, #rn + 1,
if(#t := id_type, 1, 1)
)
) as seqnum
from (select timestampdiff(second, s.date_sent, c.date_click) as time_diff,
s.id_type,
from emails_sent s inner join
emails_clicks c
on s.id = c.id_email
order by time_diff
) sc cross join
(select #t := -1, #rn := 0) as params
) sc join
(select id_type, count(*) as cnt
from emails_sent s inner join
emails_clicks c
on s.id = c.id_email
group by id_type
) n
where 2 * seqnum in (n.cnt, n.cnt, n.cnt + 1, n.cnt + 2)
group by sc.id_type;
I am trying to return a limited of number of products per brand. The tables are
brands:
id, name
products:
id, brand_id, name
What I am trying to achieve is a query that will output brands.name and products_name 10 times for each brand.
I have tried joining the two tables but when it comes to applying the limit I can't see the next step. Is this possible or will I have to opt to do the brand query first and then query again on a foreach this being more processor intensive?
Get 10 records per product from the second table by the following query:
SELECT *
FROM(
SELECT id, brand_id, name, #n := IF(#r = brand_id, #n + 1, 1) AS rownum,
#r := brand_id
FROM product, (SELECT #r := 0, #n := 0) a
ORDER BY brand_id, id
) a
WHERE a.rownum <= 10;
And join it with brand table, e.g.:
SELECT *
FROM brand b
JOIN (SELECT *
FROM(
SELECT id, brand_id, name, #n := IF(#r = brand_id, #n + 1, 1) AS rownum,
#r := brand_id
FROM product, (SELECT #r := 0, #n := 0) a
ORDER BY brand_id, id
) a
WHERE a.rownum <= 10
) p on b.id = p.brand_id;
Here's the SQL Fiddle.
How delete duplicate data except two row?
id 4 must deleted, because 'mangga' already have 3 row
This is a bit painful in MySQL. The following identifies the rows to be deleted:
select t.*
from (select t.*,
(#rn := if(#n = nama, #rn + 1,
if(#n := nama, 1, 1)
)
) as rn
from t cross join
(select #n := '', #rn := 0) params
order by nama, id
) t
where rn > 2;
You can then do the delete using a join:
delete t
from t join
(select t.*,
(#rn := if(#n = nama, #rn + 1,
if(#n := nama, 1, 1)
)
) as rn
from t cross join
(select #n := '', #rn := 0) params
order by nama, id
) tt
on t.id = tt.id
where tt.rn > 2;
My first query
SELECT
id,
year_,
month_
FROM
(SELECT
tp.id,
YEAR(FROM_UNIXTIME(tp.visited_date)) as year_,
MONTH(FROM_UNIXTIME(tp.visited_date)) as month_,
#rn := IF(#prev = CONCAT(YEAR(FROM_UNIXTIME(tp.visited_date)),MONTH(FROM_UNIXTIME(tp.visited_date))), #rn + 1, 1) AS rn,
#prev := CONCAT(YEAR(FROM_UNIXTIME(tp.visited_date)),MONTH(FROM_UNIXTIME(tp.visited_date)))
FROM
tr_place tp
JOIN
(SELECT #prev := NULL, #rn := 0) AS vars
ORDER BY
YEAR(FROM_UNIXTIME(tp.visited_date)) DESC,
MONTH(FROM_UNIXTIME(tp.visited_date)) DESC) AS T1
WHERE
rn < 3;
Will returns the data set This is the result which I got from the query
The subquery in it
SELECT
tp.id,
YEAR(FROM_UNIXTIME(tp.visited_date)) as year_,
MONTH(FROM_UNIXTIME(tp.visited_date)) as month_,
#rn := IF(#prev = CONCAT(YEAR(FROM_UNIXTIME(tp.visited_date)),MONTH(FROM_UNIXTIME(tp.visited_date))), #rn + 1, 1) AS rn,
#prev := CONCAT(YEAR(FROM_UNIXTIME(tp.visited_date)),MONTH(FROM_UNIXTIME(tp.visited_date)))
FROM
tr_place tp
JOIN
(SELECT #prev := NULL, #rn := 0) AS vars
ORDER BY
YEAR(FROM_UNIXTIME(tp.visited_date)) DESC,
MONTH(FROM_UNIXTIME(tp.visited_date)) DESC;
Returns data The sub query will returns this data
I need the subquery's greatest rn as a column in the first query.
How can I achieve that?
You may be having a problem with variable assignment. You should not be referencing variables in multiple expressions in the select. So, the correct way to write the first query is:
SELECT id, year_, month_
FROM (SELECT tp.id,
YEAR(FROM_UNIXTIME(tp.visited_date)) as year_,
MONTH(FROM_UNIXTIME(tp.visited_date)) as month_,
(#rn := IF (#prev = CONCAT(YEAR(FROM_UNIXTIME(tp.visited_date)), MONTH(FROM_UNIXTIME(tp.visited_date))), #rn,
if(#prev := CONCAT(YEAR(FROM_UNIXTIME(tp.visited_date)), MONTH(FROM_UNIXTIME(tp.visited_date))), 1, 1
)
) as rn
FROM tr_place tp JOIN
(SELECT #prev := NULL, #rn := 0) AS vars
ORDER BY YEAR(FROM_UNIXTIME(tp.visited_date)) DESC,
MONTH(FROM_UNIXTIME(tp.visited_date)) DESC
) t1
WHERE rn < 3;
Note the variable assignments are all in a single expression.
This may fix your issue.
I am trying to create a query that selects 2 random rows for each parent_id from my table.
At the moment my query always returns the first 2 id's for each parent_id. (For example: 1,2 of parent_id=1).
My table is currently as follows:
id, title , parent_id
1, Title1 , 1
2, Title2 , 1
3, Title3 , 1
4, Title4 , 2
5, Title5 , 2
6, Title6 , 2
7, Title7 , 2
8, Title8 , 3
9, Title9 , 3
10, Title10, 3
My current query is:
SELECT id,title,parent_id, rn
FROM (SELECT (#rn := if(#parent_id = parent_id, #rn + 1,
if(#parent_id := parent_id, 1, 1)
)
) as rn,
meals.*
FROM meals CROSS JOIN
(SELECT #rn := 0, #parent_id := '') params
ORDER BY rand()
) meals
WHERE rn <= 2
ORDER BY id ASC
I would like my result to change on each query so for example one result will return the id's 1,3 for parent_id=1 and one will return 2,3 and so on...
Try moving the order by rand() clause into its own derived table
SELECT id,title,parent_id, rn
FROM (SELECT (#rn := if(#parent_id = parent_id, #rn + 1,
if(#parent_id := parent_id, 1, 1)
)
) as rn,
t1.*
FROM ( SELECT * FROM meals CROSS JOIN
(SELECT #rn := 0, #parent_id := '') params
ORDER BY rand() ) t1
ORDER BY parent_id
) meals
WHERE rn <= 2
ORDER BY id ASC
http://sqlfiddle.com/#!9/3310f/1
I think you just need to add parent_id into the order by:
SELECT id, title, parent_id, rn
FROM (SELECT (#rn := if(#parent_id = parent_id, #rn + 1,
if(#parent_id := parent_id, 1, 1)
)
) as rn,
meals.*
FROM meals CROSS JOIN
(SELECT #rn := 0, #parent_id := -1) params
ORDER BY parent_id, rand()
) meals
WHERE rn <= 2
ORDER BY id ASC;
And, if parent_id is a number, there is no reason to make #parent_id a string.