Using this query I can find the Company Assignee number for company with most patents but I can't seem to print the company name.
SELECT count(*), patent.assignee
FROM Patent
GROUP BY patent.assignee
HAVING count(*) =
(SELECT max(count(*))
FROM Patent
Group by patent.assignee);
COUNT(*) --- ASSIGNEE
9 19715
9 27895
Nesting above query into
SELECT company.compname
FROM company
WHERE ( company.assignee = ( *above query* ) );
would give an error "too many values" since there are two companies with most patents but above query takes only one assignee number in the WHERE clause. How do I solve this problem? I need to print name of BOTH companies with assignee number 19715 and 27895. Thank you.
You have started down the path of using nested queries. All you need to do is remove COUNT(*):
SELECT company.compname
FROM company
WHERE company.assignee IN
(SELECT patent.assignee
FROM Patent
GROUP BY patent.assignee
HAVING count(*) = (SELECT max(count(*))
FROM Patent
GROUP BY patent.assignee
)
);
I wouldn't write the query this way. The use of max(count(*)) is particularly jarring, but it is valid Oracle syntax.
Applying an aggregate function on another aggregate function (like max(count(*))) is illegal in many databases but I believe using the ALL operator instead and a join to get the company name would solve your problem.
Try this:
SELECT COUNT(*), p.assignee, c.compname
FROM Patent p
JOIN Company c ON c.assignee = p.assignee
GROUP BY p.assignee, c.compname
HAVING COUNT(*) >= ALL -- this predicate will return those rows
( -- for which the comparison holds true
SELECT COUNT(*) -- for all instances.
FROM Patent -- it can only be true for the highest count
GROUP BY assignee
);
Assuming you have Oracle, I thought about this a bit differently:
select
c.compname
from
company c
join
(
select
assignee,
dense_rank() over (order by count(1) desc) rnk
from
patent
group by
assignee
) p
on p.assignee = c.assignee
where
p.rnk = 1
;
I like this because is lets you find the any rank. For example, if you want the top 3 you would just change p.rnk = 1 to p.rnk <= 3. If you want 10th place, you just change it to p.rnk = 10. Adding the total count and rank into the results would be easy from here too. Overall I think it's more versatile.
Related
I am trying to get a better understanding of group by and count in SQL and tried to find the student who has been studying for the second longest time.
I need to also group by s.semester for it to work, just group by s.name alone (which is what I had done initially) does not work - why is this? I know this is right, but am trying to understand why for future practice questions.
select s.name
from students s
group by s.name, s.semester
having 1 = (select count (gold.name)
from students gold
where gold.name <> s.name
and gold.semester > s.semester
)
Thanks in advance!
To solve this task, it is not enough to use grouping. You need to use ranking functions.
You will receive the rank of each subsequent student or students, based on the number of semesters.
You can get students by rank using "where".
select
*
from(
select
row_number() over (partition by name_students, semestr order by semestr_count
asc) r_n,
name_students,
semestr
from (
select name_students, semestr, count(semestr_count) from studies
group by name_students, semestr
) agregate_studies
where r_n = 1
Using r_n for get some students top _ n : 2..3
I have read in various websites about the count() function but I still cannot make this work.
I made a small table with (id, name, last name, age) and I need to retrieve all columns plus a new one. In this new column I want to display how many times a name shows up or repeats itself in the table.
I have made test and can retrieve but only COLUMN NAME with the count column, but I haven't been able to retrieve all data from the table.
Currently I have this
select a.n_showsup, p.*
from [test1].[dbo].[person] p,
(select count(*) n_showsup
from [test1].[dbo].[person])a
This gives me all data on output but on the column n_showsup it gives me just the number of rows, now I know this is because I'm missing a GROUP BY but then when I write group by NAME it shows me a lot of records. This is an example of what I need:
You can use window functions, if you RDBMS supports them:
select t.*, count(*) over(partition by name) n_showsup
from mytable t
Alternatively, you can join the table with an aggregation query that counts the number of occurences of each name:
select t.*, x.n_showsup
from mytable t
inner join (select name, count(*) n_showsup from mytable group by name) x
on x.name = t.name
While the window function approach (#GMB's answer) is the right way to go, thinking through this from a subquery approach (like you were headed towards) would look something like:
select p.*, a.n_showsup
from [test1].[dbo].[person] p
INNER JOIN (
select name, count(*) n_showsup
from [test1].[dbo].[person]
GROUP BY name
) a ON p.name = a.name
This is VERY close to what you had, the difference is that we are grouping that subquery by name (so we get a count by name) and we can use that in the join criteria which we do with the ON clause on that INNER JOIN.
You should really never ever use a comma in your FROM clause. Instead use a JOIN.
Let's say I have a bases with a table:
-courses (key: name [ofthecourse], other attributes: year in which the course takes place)
I want to complete a query looking for an answer to the question:
On which year of study there is a maximum number of courses?
Normally, the query would be:
SELECT TOP 1 STUDYEAR
FROM COURSES
GROUP BY STUDYEAR
ORDER BY COUNT(CNO) DESC;
But my question is, which query could complete this without using the TOP 1 phrase?
You can use an inner query to get the maximum count. The only difference is though that it can return more than one record if they have the same count.
SELECT STUDYEAR
FROM COURSES
GROUP BY STUDYEAR
HAVING COUNT(CNO) = (SELECT MAX(CNOCount) FROM
(SELECT COUNT(CNO) CNOCount
FROM COURSES
GROUP BY STUDYEAR) X)
Another version with only one inner query:
SELECT STUDYEAR
FROM
(SELECT STUDYEAR, ROW_NUMBER() OVER (ORDER BY COUNT(CNO) DESC) RowNumber
FROM COURSES
GROUP BY STUDYEAR) X
WHERE RowNumber = 1
I'm trying to select the latest date and group by name and keep other columns.
For example:
name status date
-----------------------
a l 13/19/04
a n 13/09/05
a dd 13/18/03
b l 13/01/01
b dd 13/01/02
b n 13/01/03
and I want the result like:
name status date
-----------------
a n 13/09/05
b n 13/01/03
Here's my code
SELECT
Name,
MAX(DATE) as Date,
Status
FROM
[ST].[dbo].[PS_RC_STATUS_TBL]
GROUP BY
Name
I know that I should put max(status) because There are a lot of possibilities in each case, and nothing in the query makes it clear which value to choose for status in each group. Is there anyway to use inner join ?
It's not clear to me you want the max or min status. Rather it seems to me you want the name and status as of a date certain. That is, you want the rows with the lastest date for each name. So ask for that:
select * from PS_RC_STATUS_TBL as T
where exists (
select 1 from PS_RC_STATUS_TBL
where name = T.name
group by name
having max(date) = T.date
)
Another way to think about it is
select T.*
from PS_RC_STATUS_TBL as T
join (
select name, max(date) as date
from PS_RC_STATUS_TBL
group by name
) as D
on T.name = D.name
and T.date = D.date
SQL Server needs to know what to do with the rows that you are not grouping on (it has multiple rows to show on 1 line - so how?). If you have aggregated on them (MIN, MAX, AVG, etc) then you are telling it what to do with these rows. If not it will not know what to do - and will give you an error like the one you are getting.
From what you are saying though - it sounds like you do not want to group by the status. It sounds like you are not interested in that column at all. Let me know If that assumption is wrong.
SELECT
Name,
MAX(Date) AS 'Date',
FROM
PS_RC_STATUS_TBL
GROUP BY
Name
If you really do want the status, but don't want to group on it - try this:
SELECT
MyTable1.Name,
MyTable2.Status,
MyTable1.Date
FROM
(SELECT Name, MAX(Date) AS 'Date' FROM PS_RC_STATUS_TBL GROUP BY Name) MyTable1
INNER JOIN
(SELECT Name, Date, Status FROM PS_RC_STATUS_TBL) MyTable2
ON MyTable1.Name = MyTable2.Name
AND MyTable1.Date = MyTable2.Date
That gives the exact results you've asked for - so does the method below using a CTE.
OR
WITH cte AS (
SELECT Name, MAX(Date) AS Date
FROM PS_RC_STATUS_TBL
GROUP BY Name)
SELECT cte.Name,
tbl.Status,
cte.Date
FROM cte INNER JOIN
PS_RC_STATUS_TBL tbl ON cte.Name = tbl.Name
AND cte.Date = tbl.Date
SQLFiddle example.
It just means that you need to put all non-aggregated columns in the GROUP BY clause, so in the case you need to put the other one
Select Name ,
MAX(DATE) as Date ,
Status
FROM [ST].[dbo].[PS_RC_STATUS_TBL] PS
Group by Name, Status
This is a common problem with text fields in SQL aggregation scenarios. Using either MAX(Status) or MIN(Status) in your field list is a solution, usually MAX(Status) because of the lexical ordering:
"" < " " < "a"
In cases where you really need a more detailed ordering:
Join to a StatusOrder relation (*Status, OrderSequence) in your main query;
select Max(OrderSequence) in your aggregated query; and
Join back to your StatusOrder relation on OrderSequence to select the correct Status value for display.
Whatever fields you're selecting other than aggregation function, need to mention in group by clause.
SELECT
gf.app_id,
ma.name as name,
count(ma.name) as count
FROM [dbo].[geo_fen_notification_table] as gf
inner join dbo.mobile_applications as ma on gf.app_id = ma.id
GROUP BY app_id,name
Here im accessing app_id and name in select, so i need to mention that after group by clause. otherwise it will throw error.
This is a simple problem, and I'm not sure if its possible here. Here's the problem:
=> http://sqlfiddle.com/#!12/584f1/7
Explanation:
A ticket belongs to an attendee
An attendee has a revenue
I need to group the tickets by section and get the total revenue.
This double counts attendees because 2 tickets can belong to the same attendee, thus double counting it. I'd like to grab the sum of the revenue, but only count the attendees once.
In my sqlfiddle example, I'd like to see:
section | total_revenue
------------------------
A | 40 <= 40 is correct, but I'm getting 50...
B | null
C | 40
I'd like to solve this without the use of sub queries. I need a scalable solution that will allow me to do this for multiple columns on different joins in a single query. So whatever allows me to accomplish this, I'm open to suggestions.
Thanks for your help.
Here is a version using row_number():
select section,
sum(revenue) Total
from
(
select t.section, a.revenue,
row_number() over(partition by a.id, t.section order by a.id) rn
from tickets t
left join attendees a
on t.attendee_id = a.id
) src
where rn = 1
group by section
order by section;
See SQL Fiddle with Demo
Again, without subquery:
Key element is to add PARTITION BY to the window function(s):
SELECT DISTINCT
t.section
-- ,sum(count(*)) OVER (PARTITION BY t.section) AS tickets_count
,sum(min(a.revenue)) OVER (PARTITION BY t.section) AS atendees_revenue
FROM tickets t
LEFT JOIN attendees a ON a.id = t.attendee_id
GROUP BY t.attendee_id, t.section
ORDER BY t.section;
-> sqlfiddle
Here, you GROUP BY t.attendee_id, t.section, before you run the result through the window function. And use PARTITION BY t.section in the window function as you want results partitioned by section this time.
Uncomment the second line if you want to get a count of tickets, too.
Otherwise, it works similar to my answer to your previous question. I.e., the rest of the explanation applies.
You can do this:
select t.section, sum(d.revenue)
from
(
SELECT DISTINCT section, attendee_id FROM tickets
) t
left join attendees d on t.attendee_id = d.id
group by t.section
order by t.section;