I have a table which records questions, their answers, and their authors. The column names are as follows:
id, question, answers, author
I would like to get a list of top 10 authors who have written the most questions. So it would need to first count the number of questions each author has written then sort them by the count then return the top 10.
This is in SQLite and I'm not exactly sure how to get the list of counts. The second part should be fairly simple as it's just an ORDER BY and a LIMIT 10. How can I get the counts into a list which I can select from?
SELECT BY COUNT(author)
,author
FROM table_name
GROUP BY author
ORDER BY COUNT(author) DESC LIMIT 10;
You can apply an order by clause to an aggregate query:
SELECT author, COUNT(*)
FROM mytable
GROUP BY author
ORDER BY 2 DESC
LIMIT 10
You could wrap your query as a subquery and then use LIMIT like this:
SELECT *
FROM (
SELECT author
,COUNT(*) AS cnt
FROM mytable
GROUP BY author
) t
ORDER BY t.cnt DESC
LIMIT 10;
Related
I am completely rewriting this question, I just cant crack it
IDB DB2 SQL
(from a Chicago Crime Dataset)
Which community area is most crome prone?
When I use this code, it does correctly count and sort the data
select community_area_number as community_area_number, count(community_area_number) as total_area_crime
from chicago_crime_data
group by community_area_number
order by total_area_crime desc;
the problem is, it lists all the data descending, but no matter what MAX statement I use, either in the select or the order by statement, it wont show just the max values.
The max values are 43, so I would like to to show both 'community_area_numbers' that have 43.
Instead it shows the entire list.
Here is a screenshot
also, yes I understand I can just do a LIMIT 2 command, but that would be cheating since I manually checked that there are 2 max values, but if this data changed or i didnt know that, it doesnt solve anything
thanks in advance
What you would be looking for is the standard SQL clause FETCH WITH TIES;
select community_area_number, count(*) as total_area_crime
from chicago_crime_data
group by community_area_number
order by total_area_crime desc
fetch first row with ties;
Unfortunately, though, DB2 doesn't support WITH TIES in FETCH FIRST.
The classic way (that is before we had the window functions RANK and DENSE_RANK) is to use a subquery: Get the maximum value, then get all rows with that maximum. I am using a CTE (aka WITH clause) here in order not to have to write everything twice.
with counted as
(
select community_area_number, count(*) as total_area_crime
from chicago_crime_data
group by community_area_number
)
select community_area_number, total_area_crime
from counted
where total_area_crime = (select max(total_area_crime) from counted);
(Please note that this is a mere COUNT(*), because we want to count rows per community_area_number.)
Like #topsail mentioned. You could use a rank function.
From the table you have above you could do the following
SELECT t.* FROM
(
SELECT *,
RANK() OVER (Order by Total_Area_Crime DESC) rnk
from
table1
)t
WHERE t.rnk = 1
db fiddle
So your full query should look something like this:
With cte AS (
SELECT MAX(COMMUNITY_AREA_NUMBER) AS COMMUNITY_AREA_NUMBER,
COUNT(COMMUNITY_AREA_NUMBER) AS TOTAL_AREA_CRIME
FROM CHICAGO_CRIME_DATA
GROUP BY COMMUNITY_AREA_NUMBER
ORDER BY TOTAL_AREA_CRIME DESC;
)
SELECT t.* FROM
(
SELECT *,
RANK() OVER (Order by Total_Area_Crime DESC) rnk
from
cte
)t
WHERE t.rnk = 1
It turns out the professor did want us to use the Limit command.
Here is the final answer:
SELECT COMMUNITY_AREA_NUMBER, COUNT(ID) AS CRIMES_RECORDED
FROM CHICAGO_CRIME_DATA
GROUP BY COMMUNITY_AREA_NUMBER
ORDER BY CRIMES_RECORDED DESC LIMIT 1;
thanks to all those who responded :D
I am having the IMDB database; I am looking for the top two years in which most movies were produced, and I have to sort them chronologically after the years and print only the years.
I am trying this to compute the list and sort it 'the other way around' afterwards but I cannot order by anthing in the last 'order by' statement because in the FROM-statement I dont refer to any tables and instead open the next statement. It says "unknown column topTwo" as well so that I cannot order my results accordingly.
What am I doing wrong?
SELECT *
FROM
(SELECT m.year, COUNT(*)
FROM movies as m
GROUP BY m.year
ORDER BY m.year DESC) AS topTwo
ORDER BY **topTwo** ASC
LIMIT 2;
I think you are looking for this:
SELECT topTwo.year
FROM (SELECT m.year, COUNT(*) as cnt
FROM movies m
GROUP BY m.year
ORDER BY COUNT(*) DESC
LIMIT 2
) topTwo
ORDER BY year ASC;
Notes:
The LIMIT goes in the subquery.
The COUNT(*) is given an alias.
The ORDER BY in the subquery is based on the count.
The ORDER BY in the outer query is based on the year.
You only seem to want the year, so the outer query only select that column.
I have this query currently, which selects the top "number of pickups" in descending order. I need to filter only the top 10 rows/highest numbers though. How can I do this?
I have tried adding 'WHERE ROWNUM <= 10' at the bottom, to no avail.
SELECT customer.company_name, COUNT (item.pickup_reference) as "Number of Pickups"
FROM customer
JOIN item ON (customer.reference_no=item.pickup_reference)
GROUP BY customer.company_name, item.pickup_reference
ORDER BY COUNT (customer.company_name) DESC;
Thanks for any help!
You need to subquery it for the rownum to work.
SELECT *
FROM
(
SELECT customer.company_name, COUNT (item.pickup_reference) as "Number of Pickups"
FROM customer
JOIN item ON (customer.reference_no=item.pickup_reference)
GROUP BY customer.company_name, item.pickup_reference
ORDER BY COUNT (customer.company_name) DESC
)
WHERE rownum <= 10
You could alternatively use ranking functions, but given the relative simplicity of this, I'm not sure whether I would.
The solution by using the rank is something like this :
select customer.company_name, COUNT (item.pickup_reference) from (
select distinct customer.company_name, COUNT (item.pickup_reference) ,
rank() over ( order by count(item.pickup_reference) desc) rnk
from customer
JOIN item ON (customer.reference_no=item.pickup_reference)
group by customer.company_name, item.pickup_reference
order by COUNT (customer.company_name) )
where rnk < 10
Using the 'rownum' to get the top result doesn't give the expected result, because it get the 10 first rows which are not ordred, and then order them (Please notify this on a comment on Andrew's response, I don't have the right to add the comment) .
I'm not sure if this is even a good question or not.
I have a complex query with lot's of unions that searches multiple tables for a certain keyword (user input). All tables in which there is searched are related to the table book.
There is paging on the resultset using LIMIT, so there's always a maximum of 10 results that get withdrawn.
I want an extra column in the resultset displaying the total amount of results found however. I do not want to do this using a separate query. Is it possible to add a count() column to the resultset that counts every result found?
the output would look like this:
ID Title Author Count(...)
1 book_1 auth_1 23
2 book_2 auth_2 23
4 book_4 auth_.. 23
...
Thanks!
This won't add the count to each row, but one way to get the total count without running a second query is to run your first query using the SQL_CALC_FOUND_ROWS option and then select FOUND_ROWS(). This is sometimes useful if you want to know how many total results there are so you can calculate the page count.
Example:
select SQL_CALC_FOUND_ROWS ID, Title, Author
from yourtable
limit 0, 10;
SELECT FOUND_ROWS();
From the manual:
http://dev.mysql.com/doc/refman/5.1/en/information-functions.html#function_found-rows
The usual way of counting in a query is to group on the fields that are returned:
select ID, Title, Author, count(*) as Cnt
from ...
group by ID, Title, Author
order by Title
limit 1, 10
The Cnt column will contain the number of records in each group, i.e. for each title.
Regarding second query:
select tbl.id, tbl.title, tbl.author, x.cnt
from tbl
cross join (select count(*) as cnt from tbl) as x
If you will not join to other table(s):
select tbl.id, tbl.title, tbl.author, x.cnt
from tbl, (select count(*) as cnt from tbl) as x
My Solution:
SELECT COUNT(1) over(partition BY text) totalRecordNumber
FROM (SELECT 'a' text, id_consult_req
FROM consult_req cr);
If your problem is simply the speed/cost of doing a second (complex) query I would suggest you simply select the resultset into a hash-table and then count the rows from there while returning, or even more efficiently use the rowcount of the previous resultset, then you do not even have to recount
This will add the total count on each row:
select count(*) over (order by (select 1)) as Cnt,*
from yourtable
Here is your answare:
SELECT *, #cnt count_rows FROM (
SELECT *, (#cnt := #cnt + 1) row_number FROM your_table
CROSS JOIN (SELECT #cnt := 0 AS variable) t
) t;
You simply cannot do this, you'll have to use a second query.
I have an SQL Query that i'm running but I only want to select a specific row. For example lets say my query was:
Select * from Comments
Lets say this returns 10 rows, I only want to select the 8th record returned by this query. I know I can do:
Select Top 5 * from Comments
To get the top 5 records of that query but I only want to select a certain record, is there anything I can put into this query to do that (similar to top).
Thanks
jack
This is a classic interview question.
In Ms SQL 2005+ you can use the ROW_NUMBER() keyword and have the Predicate ROW_NUMBER = n
USE AdventureWorks;
GO
WITH OrderedOrders AS
(
SELECT SalesOrderID, OrderDate,
ROW_NUMBER() OVER (ORDER BY OrderDate) AS 'RowNumber'
FROM Sales.SalesOrderHeader
)
SELECT *
FROM OrderedOrders
WHERE RowNumber = 5;
In SQL2000 you could do something like
SELECT Top 1 *FROM
[tblApplications]
where [ApplicationID] In
(
SELECT TOP 5 [ApplicationID]
FROM [dbo].[tblApplications]
order by applicationId Desc
)
How about
SELECT TOP 1 * FROM
(SELECT TOP 8 * FROM Comments ORDER BY foo ASC)
ORDER BY foo DESC
First, you should say which RDBMS you're using.
Second, you should give careful thought to what it is you're trying to accomplish. Relational Databases are set-based. In general, the order of elements in a set does not matter. You'll want to ask why it matters in this case, then see if there's a better way to embed the concept of order into the query itself.
For instance, in SQL Server 2005 (and other RDBMS), you can use the ROW_NUMBER function to assign a sequential number to each row returned, based on the criteria you specify. You could then select rows based on the row number. Example from Books Online:
USE AdventureWorks;
GO
WITH OrderedOrders AS
(
SELECT SalesOrderID, OrderDate,
ROW_NUMBER() OVER (ORDER BY OrderDate) AS 'RowNumber'
FROM Sales.SalesOrderHeader
)
SELECT *
FROM OrderedOrders
WHERE RowNumber BETWEEN 50 AND 60;
SELECT * FROM comments WHERE ...conditions... LIMIT 1 OFFSET 8
OFFSET is a good thing for MySQL
For SQL Server 2005:
select rank() OVER (ORDER BY c.subject, c.date) as rank, c.subject, c.date
from comments c
where rank = 8
Well, in T-SQL (the dialect for SQL Server) you can do the following:
SELECT TOP 1 *
FROM (SELECT TOP 8 *
FROM Table
ORDER
BY SortField)
ORDER
BY SortField DESC
This way you get the 8th record.
I have read the question & your comments on you would want next 3 blog comments etc.
How is your tables structured?
Assume that you have blog post Id & comment Id is generated in ascending order for each blog post, you could do a SELECT based on the current Id.
e.g. if the blogpostId = 101, you get the top 3 comments order by posted Id. Now lets say, you want to get the next 3 comments - you could do a SELECT WHERE commentId between the last comment id shown TO the comment id - 3
But all that depends on how your tables are defined.
In SQL 2000 where you do not have ROW_NUMBER() function you could use a work-around like this:
SELECT CommentsTableFieldList, IDENTITY(INT, 1,1) as seqNo
INTO #SeqComments
FROM Comments
SELECT * FROM #SeqComments
WHERE seqNo = 8
select top 1 *
from TableName
where ColumnName1 in
(
select top nth ColumnName1
from TableName
order by ColumnName1 desc
)
order by ColumnName1 desc
From the SELECT reference, use the LIMIT keyword:
SELECT * FROM tbl LIMIT 5,10; # Retrieve rows 6-15
SELECT * FROM tbl LIMIT 5; # Retrieve first 5 rows
Note: this is for MySQL, other SQL engines may have a different keyword.
Select from tablename limit nthrow,1;
try This
Let us assume , We want select 5th row of WC_Video Table
And
Select * from (Select Row_Number() over (Order by Uploadedon) as 'rownumber',* from Wc_Video )as Temp where rownumber=5