Guy I am trying to ranking some data from my database, and I notice that it's going very wrong when I put the group by clause;
SET #rank=0;
SELECT #rank:=#rank+1 AS RankSemGenero
,a.nome AS Artista
,f.nome AS Musica
,SUM(rnk.total) AS Tocadas
,rnk.mes AS Mes
,rnk.dia AS Dia
,current_timestamp() AS Criado_Em_Sem_Genero
,23 AS RankComGenero
,current_timestamp() AS Criado_Em_Com_Genero
/*,CASE rnk.categoria
WHEN 1 then 'AM'
WHEN 2 then 'FM'
WHEN 3 then 'Web'
WHEN 4 then 'Comunitaria'
END AS Categoria_Radio*/
,'Todas' AS TipoEmissora
,5 AS Relevancia_Emissora
,'Nacional' AS Local
,5 AS Relevancia_Local
,1 AS fl_ativo
FROM rnk201901 rnk
LEFT JOIN artistas a ON rnk.artista = a.id
LEFT JOIN fonogramas f ON rnk.fonograma = f.id
WHERE rnk.dia = 10
-- AND rnk.fonograma = 35876
-- GROUP BY rnk.fonograma
ORDER BY rnk.total DESC;
This code above bringing the information on the right way 1 until ....
But if I change the GROUP BY line, I am receiving something like: 1700 instead of 1.
GROUP BY rnk.fonograma
Any idea how to handle this group by counting 1 by 1?
Thanks!!
You need to use a subquery, when using variables with group by:
select (#rank := #rank + 1) as rank, t.*
from (<your aggregation query here with order by>) t cross join
(select #rank := 0) params;
Related
I have this following table:
name value year
A 1 2015
A 2 2014
A 3 2013
B 1 2015
B 3 2013
C 1 2015
C 2 2014
How can I get, for each name, the row with the second highest year, like this:
name value year
A 2 2014
B 3 2013
C 2 2014
I tried the following query but no success:
select name, value, year
from TABLE_NAME
WHERE year IN (select year from TABLE_NAME order by year desc limit 1,1)
The previous query gives me this error:
"SQL Error (1235): This version of MySQL doesn't yet support 'LIMIT & IN/ALL/ANY/SOME subquery' "
And I can't change the MySQL version (5.6.25) right now, because the solution is already in production.
Any help, please?
One way to solve n per group in MySQL is to simulate ROW_NUMBER. Note that this will only return one value per name.
SELECT
name,
value,
year
FROM
(SELECT
t.name,
t.value,
t.year,
#rn := if(#prev = t.name, #rn + 1,1) as rn,
#prev:=t.name
FROM
test_table as t
JOIN (SELECT #Prev:= Null, #Rn := 0) as v
ORDER BY
t.name,
T.year desc) as t
WHERE
rn = 2;
How this works.
SELECT #Prev:= Null, #Rn := 0 initializes two variables #Prev and #Rn.
#rn := if(#prev = t.name, #rn + 1,1) as rn set the variable of #rn to either 1 or #rn + 1 depending on if #prev = t.Name and returns the value of #rn as the column rn
#prev:=t.name sets the value of #prev equal to the current value of name
if you run
SELECT
t.name,
t.value,
t.year,
#prev = t.name as eval,
#rn := if(#prev = t.name, #rn + 1,1) as rn,
#prev:=t.name as prev
FROM
test_table as t
JOIN (SELECT #Prev:= Null, #Rn := 0) as v
ORDER BY
t.name,
T.year desc
I would expect something like
name value year eval rn prev
A 1 2015 false 1 null
A 2 2014 true 2 A
A 3 2013 true 3 A
B 1 2015 false 1 A
B 3 2013 true 2 B
C 1 2015 false 1 B
C 2 2014 true 2 C
Wrapping into a subquery and the filtering for rn=2 gives you the desired result
My strategy is to use a grouping to find the highest years. Then join with the original table to remove the highest years. Finally do a grouping on the combined table to find the second highest year for each name. (If you need value you can do an INNER JOIN with the original table to find it.)
SELECT name, MAX(year)
FROM
(SELECT name, year
FROM TABLE_NAME) AS x1
INNER JOIN
(SELECT name, MAX(year) AS year
FROM TABLE_NAME
GROUP BY name, year
) AS x2
ON x1.name = x2.name AND x1.year <> x2.year
GROUP BY name
ORDER BY name ASC ;
Try this :
select * from test_table where year = (select distinct year from test_table order by year desc limit 1,1)
It should work if you rewrite it as a join:
select b.name, b.value, b.year
from (select year
from table_name
order by year desc
limit 1, 1) a
join table_name b
on b.year = a.year
I have the following structure in my user table:
id(INT) registered(DATETIME)
1 2016-04-01 23:23:01
2 2016-04-02 03:23:02
3 2016-04-02 05:23:03
4 2016-04-03 04:04:04
I want to get the total (accumulated) user count per day, for all days in DB
So result should be something like
day total
2016-04-01 1
2016-04-02 3
2016-04-03 4
I tried some sub querying, but somehow i have now idea how to achieve this with possibly 1 SQL statement. Of course if could group by per day count and add them programmatically, but i don't want to do that if possible.
You can use a GROUP BY that does all the counts, without the need of doing anything programmatically, please have a look at this query:
select
d.dt,
count(*) as total
from
(select distinct date(registered) dt from table1) d inner join
table1 r on d.dt>=date(r.registered)
group by
d.dt
order by
d.dt
the first subquery returns all distinct dates, then we can join all dates with all previous registrations, and do the counts, all in one query.
An alternative join condition that can give some improvements in performance is:
on d.dt + interval 1 day > r.registered
Not sure why not just use GROUP BY, without it this thing will be more complicated, anyway, try this;)
select
date_format(main.registered, '%Y-%m-%d') as `day`,
main.total
from (
select
table1.*,
#cnt := #cnt + 1 as total
from table1
cross join (select #cnt := 0) t
) main
inner join (
select
a.*,
if(#param = date_format(registered, '%Y-%m-%d'), #rowno := #rowno + 1 ,#rowno := 1) as rowno,
#param := date_format(registered, '%Y-%m-%d')
from (select * from table1 order by registered desc) a
cross join (select #param := null, #rowno := 0) tmp
having rowno = 1
) sub on main.id = sub.id
SQLFiddle DEMO
I want to the latest results for my patients. The following sql returns 69,000 results after 87 seconds in mysqlworkbench. I have made both 'date' and 'patientid' columns as index.
select Max(date) as MaxDate, PatientID
from assessment
group by PatientID
I think my table has approximately 440,000 in total. Is it because that my table is 'large'?
Is there a way to increase the speed of this query, because I will have to embed this query inside other queries. For example like below:
select aa.patientID, assessment.Date, assessment.result
from assessemnt
inner join
(select Max(date) as MaxDate, PatientID
from assessment
group by PatientID) as aa
on aa.patientID = assessment.patientID and aa.MaxDate = assessment.Date
The above will give me the latest assessment results for each patient. Then I will also embed this piece of code to do other stuff... So I really need to speed up things. Anyone can help?
I wonder if this version would have better performance with the right indexes:
select a.patientID, a.Date, a.result
from assessemnt a
where a.date = (select aa.date
from assessment aa
where aa.patientID = a.patientID
order by aa.date desc
limit 1
);
Then you want an index on assessment(patientID, date).
EDIT:
Another approach uses an index on assessment(patient_id, date, result):
select a.*
from (select a.patient_id, a.date, a.result,
(#rn := if(#p = a.patient_id, #rn + 1,
if(#p := a.patient_id, 1, 1)
)
) as rn
from assessment a cross join
(select #p := -1, #rn := 0) params
order by patient_id desc, date desc
) a
where rn = 1;
I have tables as follows:
Car(id, make, ....)
Deal(id,datetime,car_id,....)
I want to write a query that would return a year, and a car make for the cars that have the most deals (ie the most deal ids) and the number of deals for that car make.
I started out,
SELECT YEAR(D.datetime) AS the_year, C.make, COUNT(D.id) AS num
FROM Deal D, Car C
WHERE D.car_id=C.id
GROUP BY the_year
Unfortunately, this has returned the year and the total number of deals.
So I am thinking to create this within another table and then call MAX(tbl.num), but I am confused on the syntax.
Can somebody help me out please?
This is an interesting problem. What you are looking for is specifically called the "mode" in statistics. In MySQL, you would get this by using variables or the group_conat()/substring_index()` trick. I'll show the latter:
SELECT the_year,
substring_index(group_concat(cd.make order by num desc), ',', 1) as the_mark
FROM (SELECT YEAR(D.datetime) AS the_year, C.make, COUNT(D.id) AS num
FROM Deal D JOIN
Car C
ON D.car_id = C.id
GROUP BY the_year, c.make
) cd
GROUP BY the_year;
EDIT:
The version using variables:
SELECT the_year,
substring_index(group_concat(cd.make order by num desc), ',', 1) as the_mark
FROM (SELECT YEAR(D.datetime) AS the_year, C.make, COUNT(D.id) AS num,
#rn := if(#year = YEAR(D.datetime), #rn + 1, 1) as rn,
#year := YEAR(D.datetime)
FROM Deal D JOIN
Car C
ON D.car_id = C.id CROSS JOIN
(SELECT #year := 0, #rn := 0) vars
GROUP BY the_year, c.make
ORDER BY the_year, num DESC
) cd
WHERE rn = 1;
Evening,
I am trying to get an output of rows that are limited to n per group in MySQL. I can get it to work without joins, but with it I am just shy. I've pasted a dump of the relevant tables here:
http://pastebin.com/6F0v1jhZ
The query I am using is:
SELECT
title, catRef, RowNum, pCat, tog
FROM
(
SELECT
title, catRef,
#num := IF(#prevCat=catRef,#num+1,1) AS RowNum,
#prevCat AS tog,
#prevCat := catRef AS pCat
FROM (select #prevCat:=null) AS initvars
CROSS JOIN
(
SELECT p.title, oi.catRef
FROM resources p
INNER JOIN placesRel v ON (p.resId = v.refId)
INNER JOIN catRel oi ON (p.resId = oi.refId)
WHERE p.status = 'live' AND v.type = 'res' AND oi.type = 'res'
) AS T
) AS U
WHERE RowNum <= 5
ORDER BY catRef
I just can't get the row count to go up. Or any other solution would be greatly appreciated.
I'm looking for a result like this:
title catRef RowNum
Title1 1 1
Title2 1 2
Title3 1 3
Title4 2 1
Title5 2 2
Title6 3 1
At the moment, the RowNum column is always 1.
This works:
SET #num := 1, #prevCat := 0;
SELECT title, start, end, type, description, linkOut, outType, catRef, row_number
FROM (
SELECT title, start, end, type, description, linkOut, outType, catRef,
#num := if(#prevCat = catRef, #num + 1, 1) as row_number,
#prevCat AS tog,
#prevCat := catRef AS dummy
FROM (
SELECT title, start, end, resources.type, description, linkOut, outType, catRef
FROM resources LEFT JOIN placesRel ON placesRel.refId = resId LEFT JOIN catRel ON catRel.refId = resId
WHERE status = 'live' AND placesRel.type = 'res' AND catRel.type = 'res'
ORDER BY catRef
) AS w
) AS x WHERE x.row_number <= 4;
You need to put your joined query in a sub-query and order it by the column you want to group by. Use it's parent query to add row numbers. Then, the top-level query glues it all together.
If you don't put your joined query in it's own sub-query, the results won't be ordered as you wish, but instead will come out in the order they are in the database. This means the data is not grouped, so row numbers will no be applied to ordered rows.