The question is to create a view called NumberOfCities_v. And then use the view to list
countries that have more than 20 cities in the descending order of number of cities.
This is my create a view statement:
CREATE VIEW NumberOfCities_v AS
SELECT
country.code as "Country Code",
country.name as Country,
count(countrycode) as "Number Of Cities"
FROM
city,
country
WHERE
city.countrycode = country.code
GROUP BY country.code, country.name
HAVING COUNT(countrycode) > 20
ORDER BY COUNT(countrycode) desc;
I don't get any records, but I think I've created the view. According to my powerpoint, I should be getting both. Apparently I have some field errors with that statement with I try to select the view with another statement. But When I use the exact statement without the create view, I get the results I need. Can someone explain why that is?
You need to fire sql query:
Select * from `NumberOfCities_v`
to get all the records generated in view.
Related
I have a mySQL table with 100 rows and 6 columns namely ; full_name, name, score, city, gender, rating. I want the output as one column containing distinct city values (there are only 5 distinct cities initially & the user input value of his/her city will be added, namely; Delhi, Mumbai, Patna, Chennai ,Pune) and the second column having their respective avg score.
The database is linked to the python code which I am working on & use takes input which is stored in the above 6 columns. Then according to the user request, the output as analysis is showed as graphs using matplotlib. But I am really stuck at this part where I need to show a graph having X-VALUES as city names and Y-VALUES as respective avg score for that, I need to know the query to get such an output in mySQL where we get 2 columns storing the above.
How do I do it ?
SELECT city AS X,AVG(score) AS Y
FROM yourtable GROUP BY city
Is this, what you ment? Or if you want the result as one row, you add GROUP_CONCAT:
SELECT GROUP_CONCAT(X) AS gX,GROUP_CONCAT(Y) AS gY FROM
(SELECT city AS X,AVG(score) AS Y
FROM yourtable GROUP BY city) g
ok, redbull helps...
correct syntax :
select city, avg(score) from data group by city;
wrong syntax (what I was trying to do earlier) :
select data.distinct(city), data.avg(score) , check.check_city from data, (select name, distinct(city) as check_city from data) check where data.name = check.name and data.city in check.check_city;
Thanks Anyway !
I want to get data from table in a single row for single county. Right now as shown in images it shows Different rows for Single county as Kalamazoo. It should show single with both records in single row.
I am using following query
SELECT County, Virus, SumOfPositiveTests
FROM StatewiseData
WHERE State = 'MICHIGAN'
I want the results to be shown as following
County Virus SUMOFPOSITIVETESTS
---------------------------------------------
Kalamazoo H3N2,H3N8 3
Total sum of both H3N2 and H3N8
use MYSQL GROUP_CONCAT
The following MySQL statement will return a list of comma(,) separated 'Virus's for each group of 'County' from the StatewiseData table
SELECT County,GROUP_CONCAT(Virus),sum(SumOfPositiveTests) FROM StatewiseData where State='MICHIGAN' group by County
Try this if you are using mysql:
SELECT country, GROUP_CONCAT(virus) _virus, SUM(SumofPositiveTests) as TotalPostitiveTest
FROM StatewiseData
WHERE Country = 'Kalamzoo'
GROUP BY Country
Please mind that this will not work with most databases, as they need you to to specify only the grouping field and aggregate functions of other fields in your query.
Here is the source
Try this. this would work on IBM DB2 and MySQL. what DB you are using
SELECT DISTINCT Country, Virus,SumOfPositiveTests FROM Customers where State='MICHIGAN' group by Country;
why are you using state in where condition? (please provide list of columns do you have in a column if i missed something)
if you are only selecting the country then it should be as simple as:
SELECT County,Virus,SumOfPositiveTests FROM StatewiseData where Country='Kalamzoo'
if you want to select summary or totals of single country then you you should use sum like:
SELECT country, SUM(SumofPositiveTests) as TotalPostitiveTest
FROM StatewiseData WHERE Country='Kalamzoo' GROUP BY Country
so I have a table I want to create a view with, but not entirely sure how to go about it..
So lets say we have a table with:
Index
Country
City
Population
and I want to make a view showing each country and the sum of it's population, it sounds easy, but I am having trouble wrapping my head around the SELECT used to create the view.
Just standard mySQL if it makes any difference. Thanks!
For MySQL could be something like:
SELECT country, SUM(population) as total_population
FROM table
GROUP BY country
To create a view in MYSQL:
CREATE VIEW v_country_population
AS
SELECT country, SUM(population) as total_population
FROM cities
GROUP BY country
I've got a table with 11 columns and I want to create a query that removes the rows with duplicate names in the Full Name's column but keeps the row with the lowest value in the Result's column. Currently I have this.
SELECT
MIN(sql363686.Results2014.Result),
sql363686.Results2014.Temp,
sql363686.Results2014.Full Name,
sql363686.Results2014.Province,
sql363686.Results2014.BirthDate,
sql363686.Results2014.Position,
sql363686.Results2014.Location,
sql363686.Results2014.Date
FROM
sql363686.Results2014
WHERE
sql363686.Results2014.Event = '50m Freestyle'
AND sql363686.Results2014.Gender = 'M'
AND sql363686.Results2014.Agegroup = 'Junior'
GROUP BY
sql363686.Results2014.Full Name
ORDER BY
sql363686.Results2014.Result ASC ;
At first glance it seems to work fine and I get all the correct values, but I seem to be getting a different (wrong) value in the Position column then what I have in my database table. All other values seem to be right. Any ideas on what I'm doing wrong?
I'm currently using dbVisualizer connected to a mysql database. Also, my knowledge and experience with sql is the bare mimimum
Use group by and a join:
select r.*
from sql363686.Results2014 r
(select fullname, min(result) as minresult
from sql363686.Results2014 r
group by fullname
) rr
on rr.fullname = r.fullname and rr.minresult = r.minresult;
You have fallen into the trap of the nonstandard MySQL extension to GROUP BY.
(I'm not going to work with all those fully qualified column names; it's unnecessary and verbose.)
I think you're looking for each swimmer's best time in a particular event, and you're trying to pull that from a so-called denormalized table. It looks like your table has these columns.
Result
Temp
FullName
Province
BirthDate
Position
Location
Date
Event
Gender
Agegroup
So, the first step is to locate the best time in each event for each swimmer. To do this we need to make a couple of assumptions.
A person is uniquely identified by FullName, BirthDate, and Gender.
An event is uniquely identified by Event, Gender, Agegroup.
This subquery will get the best time for each swimmer in each event.
SELECT MIN(Result) BestResult,
FullName,BirthDate, Gender,
Event, Agegroup
FROM Results2014
GROUP BY FullName,BirthDate, Gender, Event, Agegroup
This gets you a virtual table with each person's fastest result in each event (using the definitions of person and event mentioned earlier).
Now the challenge is to go find out the circumstances of each person's best time. Those circumstances include Temp, Province, Position, Location, Date. We'll do that with a JOIN between the original table and our virtual table, like this
SELECT resu.Event,
resu.Gender,
resu.Agegroup,
resu.Result,
resu.Temp.
resu.FullName,
resu.Province,
resu.BirthDate,
resu.Position,
resu.Location,
resu.Date
FROM Results2014 resu
JOIN (
SELECT MIN(Result) BestResult,
FullName,BirthDate, Gender,
Event, Agegroup
FROM Results2014
GROUP BY FullName,BirthDate, Gender, Event, Agegroup
) best
ON resu.Result = best.BestResult
AND resu.FullName = best.FullName
AND resu.BirthDate = best.BirthDate
AND resu.Gender = best.Gender
AND resu.Event = best.Event
AND resu.Agegroup = best.Agegroup
ORDER BY resu.Agegroup, resu.Gender, resu.Event, resu.FullName, resu.BirthDate
Do you see how this works? You need an aggregate query that pulls the best times. Then you need to use the column values in that aggregate query in the ON clause to go get the details of the best times from the detail table.
If you want to report on just one event you can include an appropriate WHERE clause right before ORDER BY as follows.
WHERE resu.Event = '50m Freestyle'
AND resu.Gender = 'M'
AND resu.Agegroup = 'Junior'
I am hoping someone will be able to point me in the right direction.
I have a COUNTRY table, containing a primary ID, and country name (e.g. France)
I have a second table PAYMETHODS_COUNTRIES, which contains a primary id, payment method id (e.g. 4) and country id
I am trying to output a list of checkboxes on each payment method, to control which countries (or users in which countries) have access to those local payment methods.
I have the checkbox list working okay, and the processing of the form is also working. The last remaining thing, is to output the list of country checkboxes with selected countries (e.g. this payment method is available in France and Germany) shown as CHECKED.
So what I am trying to do is to output a complete list of all countries
SELECT id, name FROM country ORDER BY id ASC
And then include the PAYMETHODS_COUNTRIES table something like this (not working of course)
SELECT country.id AS countryid,
country.name AS countryname,
paymethods_countries.id AS methodid
FROM country LEFT JOIN `paymethods_countries`
ON country.id = paymethods_countries.country
WHERE paymethods_countries.paymethod = 10
This example query only shows rows that actually have a record in PAYMETHODS_COUNTRIES, not what I am after.
What I was hoping for, is a complete list of country.id + country.name, with a final field (the ID of the PAYMETHODS_COUNTRIES table) - which should be null where there is no link. That way I should be able to check for null or otherwise, and output CHECKED for those rows.
Hopefully that makes sense - or if anyone knows a better way to achieve what I am doing, your thoughts are appreciated.
While the other answer here will produce the desired result, semantically it is more correct to move the condition from the WHERE clause to the ON clause:
SELECT country.id AS countryid,
country.name AS countryname,
paymethods_countries.id AS methodid
FROM country
LEFT JOIN `paymethods_countries`
ON country.id = paymethods_countries.country and paymethods_countries.paymethod = 10
This eliminates the need to add the extra OR condition in the WHERE clause.
It's only coming back with rows that have record in PAYMETHODS_COUNTRIES because of your WHERE clause since you say the paymethod must = 10. Add an OR to let it be null too:
SELECT country.id AS countryid,
country.name AS countryname,
paymethods_countries.id AS methodid
FROM country
LEFT JOIN `paymethods_countries`
ON country.id = paymethods_countries.country
WHERE paymethods_countries.paymethod = 10
OR paymethods_countries.paymethod IS NULL