I need to identify rows where a certain value is repeated. Here is a sample table:
COUNTRY CITY
Italy Milan
Englad London
USA New York
Canada London
USA Atlanta
The query should return...
COUNTRY CITY
Englad London
Canada London
...because London is repeated. Thank you in advance for your help.
The easiest way is to use a subquery that counts the number of times each city appears (and filter to those values that appear more than once):
SELECT * FROM Cities
WHERE City in
(
SELECT City FROM Cities
GROUP BY City
HAVING COUNT(*) > 1
)
If your DBMS supports windowed aggregates.
SELECT COUNTRY,
CITY
FROM (SELECT COUNTRY,
CITY,
COUNT(*) OVER (PARTITION BY CITY) AS Cnt
FROM Cities) T
WHERE Cnt > 1
SQL Fiddle
select country, city
from aTable
where city in
(
select city
from aTable
group by city
HAVING count(1) > 1
)
Try it here: http://sqlfiddle.com/#!3/e9b1a/1
Or if the same city & country combo appears twice and you're only interested where the countries are different:
select distinct country, city
from aTable
where city in
(
select city
from aTable
group by city
HAVING count(distinct country) > 1
)
Try it here: http://sqlfiddle.com/#!3/2dfaa/2
This one works. Got it from my wife (she finally had time to look into this). Thought you might be interested.
SELECT * FROM Cities
WHERE City in ( select city
from (SELECT City,
count(distinct country)
FROM Cities
GROUP BY City
HAVING count(distinct country) > 1) a )
Related
I have this table:
first_name
last_name
age
country
John
Doe
31
USA
Robert
Luna
22
USA
David
Robinson
22
UK
John
Reinhardt
25
UK
Betty
Doe
28
UAE
How can I get only the names of the oldest per country?
When I do this query
SELECT first_name,last_name, MAX(age)
FROM Customers
GROUP BY country
I get this result:
first_name
last_name
MAX(age)
Betty
Doe
31
John
Reinhardt
22
John
Doe
31
But I want to get only first name and last name without the aggregate function.
If window functions are an option, you can use ROW_NUMBER for this task.
WITH cte AS (
SELECT *,
ROW_NUMBER() OVER(PARTITION BY country ORDER BY age DESC) AS rn
FROM tab
)
SELECT first_name, last_name, age, country
FROM cte
WHERE rn = 1
Check the demo here.
It sounds like you want to get the oldest age per country first,
SELECT Country, MAX(age) AS MAX_AGE_IN_COUNTRY
FROM Customers
GROUP BY Country
With that, you want to match that back to the original table (aka a join) to see which names they match up to.
So, something like this perhaps:
SELECT Customers.*
FROM Customers
INNER JOIN
(
SELECT Country, MAX(age) AS MAX_AGE_IN_COUNTRY
FROM Customers
GROUP BY Country
) AS max_per_country_query
ON Customers.Country = max_per_country_query.Country
AND Customers.Age = max_per_country_query.MAX_AGE_IN_COUNTRY
If your database supports it, I prefer using the CTE style of handling these subqueries because it's easier to read and debug.
WITH cte_max_per_country AS (
SELECT Country, MAX(age) AS MAX_AGE_IN_COUNTRY
FROM Customers
GROUP BY Country
)
SELECT Customers.*
FROM Customers C
INNER JOIN cte_max_per_country
ON C.Country = cte_max_per_country.Country
AND C.Age = cte_max_per_country.MAX_AGE_IN_COUNTRY
Imagine a table below:
I want to get the total population in each country but also I'd like to see the name of a city if that city is the only city in the country.
I could run something like
select
min(Country),
listagg(City) within group as City,
sum(Population) as Population
from table1
group by Country
but what i want is ('MULTIPLE' is just an example of text I'd like to see instead of the list of cities)
How can I do that?
I haven't been able to find any solution and my only idea is to use CASE with COUNT but it won't work
P.S. Sorry for the formatting
Just count the cities or compare min and max city:
select
country,
case when min(city) = max(city) then min(city) else 'multiple' as city,
sum(population) as population
from cities
group by country
order by country;
Assuming you won't have same city appearing twice
CODE 1
WITH list_of_cities_ as (
SELECT
COUNTRY,
city,
count(city) over (partition by country) AS TOTAL_Cities,
SUM(POPULATION) over (partition by country) AS TOTAL_POPULATION
FROM table_
)
select
DISTINCT
country,
case when TOTAL_Cities > 1 THEN 'Multiple' Else city end as city,
TOTAL_POPULATION
from list_of_cities_
CODE 2
IF you are interested in getting the list of all cities, instead of keyword
"Multiple"
https://dbfiddle.uk/?rdbms=postgres_9.5&fiddle=68efe08ab72ef63afa5813925e7f99e0
SELECT
COUNTRY,
STRING_AGG(City,',') as LIST_OF_CITIES,
SUM(POPULATION) AS TOTAL_POPULATION
FROM table_
GROUP BY 1
I'm trying to count the occurrences of a distinct set of cities and countries in a user table.
The table is set out similar to:
userid city country
------ --------- --------------
1 Cambridge United Kingdom
2 London United Kingdom
3 Cambridge United Kingdom
4 New York United States
What I need is a list of every city, country pair with the number of occurrences:
Cambridge, United Kingdom, 2
London, United Kingdom, 1
New York, United States, 1
Currently I run an SQL query to get the distinct pairs:
$array = SELECT DISTINCT city, country FROM usertable
then read it into an array in PHP, and loop through the array, running a query to count each occurrences for each row in the array:
SELECT count(*) FROM usertable
WHERE city = $array['city']
AND country = $array['country']
I'm assuming my scant grasp of SQL is missing something - what would be the correct way to do this, preferably without the intervention of PHP?
select city, country, count(*)
from usertable
group by city, country
What you need is a group by:
Select city, country, count(*) as counter
from usertable
group by city, country
SELECT cityandcountry, count(*) as occurrences FROM (
SELECT DISTINCT concat(city, country) FROM tablename
) as baseview;
if you want city and country preformated, or
SELECT cityandcountry, count(*) as occurrences FROM (
SELECT DISTINCT city, country FROM tablename
) as baseview;
if not.
I have the following table that contains the following data:
http://img513.imageshack.us/img513/9039/mycities.png
The CREATE statement and the inserts are at http://snipt.org/xoKl .
The table is a list of cities and each city belongs to a region and a country and each city has a founding date. The goal here is to get for each "Country / Region" pair a list of the oldest cities. We need the oldest city on the east coast of Canada, the oldest city on the west coast of the U.S and so on ...
The query that I use right now is:
SELECT * FROM MyCities
INNER JOIN
(SELECT Country, Region, MIN(FoundingDate) AS CityFoundingDate
FROM MyCities
GROUP BY Country, Region ) AS subquery
ON subquery.CityFoundingDate = MyCities.FoundingDate
AND MyCities.Country = subquery.Country
AND MyCities.Region = subquery.Region
I just want to know whether there are other ways to write this group by query or not. :-)
Is this query efficient or not?
Looking forward to a discussion.
What about?
select country, region, city from MyCities mc1
where foundingDate <= ALL (
select foundingDate from MyCities as mc2
where mc1.country = mc2.country and mc1.region = mc2.region
)
How about something like this?
Should work in Oracle (although I can't test it right now)
SELECT country, region, city, foundingdate
FROM (
SELECT country, region, city, foundingdate, MIN(founding_date) OVER PARTITION BY (country, region) min_date
FROM mycities) WHERE foundingdate=min_date
But what if there are two cities founded on the same year in the same country/region?
I have a table with all U.S. zip codes. each row contains the city and state name for the zip code. I'm trying to get a list of cities that show up in multiple states. This wouldn't be a problem if there weren't X amount of zip codes in the same city...
So basically, I just want to the city in a state to count as 1 instead of it counting the city/state 7 times because there are 2+ zip codes in that city/state...
I'm not really sure how to do this. I know I need to use count but how do I tell the mysql to only count a given city/state combo as 1?
SELECT City, Count(City) As theCount
FROM (Select City, State From tblCityStateZips Group By City, State) As C
GROUP By City
HAVING COUNT Count(City) > 1
This would return all cities, with count, that were contained in more than one state.
Greenville 39
Greenwood 2
GreenBriar 3
etc.
First group on state and city, then group the result on city:
select City
from (
select State, City
from ZipCode
group by State, City
) x
group by City
having count(*) > 1
Will this do the trick
Select CityName, Count (Distinct State) as StateCount
From CityStateTable
Group by CityName
HAVING Count (Distinct State) > 1
Try using a select distinct
SELECT DISTINCT city, state FROM table GROUP BY city
You probably should have created a separate table for zip codes then to avoid the duplication.
You want to look into the GROUP BY Aggregate.