I have 2 tables: country and trip.
A trip can have up to 3 country codes.
country table
country_code
country_name
FRA
FRANCE
IRL
IRELAND
JPN
JAPAN
MAR
MOROCCO
NZL
NEW ZEALAND
trip table
trip_id
country_code
country_code2
country_code3
1
FRA
IRL
JPN
2
MAR
NZL
My goal is to have country names displayed on the trip table instead of country codes.
I succeed to have only 1 country code replaced, thanks to the left join clause. I would like to have up to 3 country names displayed per row.
SELECT trip_id, country_name
FROM trip
LEFT JOIN country ON country_code = country_name
The actual output of the trip table:
trip_id
country_name
1
FRANCE
2
MOROCCO
Is there a way to replace each country code with its corresponding country name?
The EXPECTED output of the query from the trip table:
trip_id
country_name
country_name2
country_name3
1
FRANCE
IRELAND
JAPAN
2
MOROCCO
NEW ZEALAND
Thank you!
You could add two more joins
SELECT trip_id, c1.country_name, c2.country_name, c3.country_name
FROM trip t
left join
country c1
on t.country_code = c1.country_code
left join
country c2
on t.country_code2 = c2.country_code
left join
country c3
on t.country_code3 = c3.country_code
The cleanest way of accomplishing this query is using subqueries:
SELECT t.trip_id,
(SELECT country_name FROM country WHERE country_code = t.country_code) "c1",
(SELECT country_name FROM country WHERE country_code = t.countty_code2) "c2",
(SELECT country_name FROM country WHERE country_code = t.country_code3) "c3"
FROM trip t
Related
I have 3 different tables, country, city, and customer. Tables are shown below:
country table:
id country_name
1 UK
2 US
3 Brazil
:
n Canada
city table
id city_name postal_code country_id
1 London 30090 1
2 Dallas 20909 2
3 Rio 29090 3
4 Atlanta 30318 2
:
n Vancouver 32230 n
customer table
id customer_name city_id
1 John 1
2 Pete 3
3 Dave 2
4 May 2
5 Chuck 4
6 Sam 3
7 Henry 3
***country.id is references city.country_id, and city.id is references customer.city_id
I want to write a query that can extract the country name, city name and the count of the customer of the associate city. But with one condition, the query will return all cities with more customers than the average number of customers of all cities
It will look something like below, this is the correct output
UK London 2
Brazil Rio 3
but I kept getting this output, which isn't correct
UK London 2
US Dallas 2
US Atlanta 1
Brazil Rio 3
I fixed my SQL query but it doesn't give me the result that I want
SELECT country.country_name, city.city_name, COUNT(customer.city_id) from country
JOIN city on country.id = city.country_id
JOIN customer on city.id = customer.city_id
Group by city_name,country.country_name;
I am wondering how can I do this and fix my code?
add country.country_name in group by
SELECT country.country_name, city.city_name, COUNT(customer.city_id) from country
JOIN city on country.id = city.country_id
JOIN customer on city.id = customer.city_id
Group by city_name,country.country_name
You are missing country.country_name in the query it will give you error. As a general rule all columns on which aggregate function is not applied should be part of group by clause.
So either you write your query without country_name in the select or add country_name in the group by clause.
In a SQL join, table 1 contains person info with city and table 2 contains city matched to country such as:-
Table #1
ID Name City
-------------------------
1 Kishan Pokhara
2 Ram Delhi
3 Shyam Beijing
Table #2
City Country
----------------------
Pokhara Nepal
Delhi India
I want to get the person ID, Name, Country so while joining the tables I want these items and if there is no country available for a city, I want "Unavailable" written in the country columns. Thanks
Try the below using left join and use coalesce() function to replace null country as 'Unavailable'
select id, name, a.city,coalesce(country,'Unavailable') as country
from table1 a left join table2 b on a.city=b.city
The question asked to take the city with the highest sum of goods that bought by customer for each country. Basically, there are cities that have the same number of goods, but we only keep the first one in alphabetical order. The result only contains country name, the city with highest number of goods and their goods in sum.
Table Schema:
Country table:
country_name
city_name
Goods table:
city_name
user_id
number_of_goods
My queries result:
France Paris 85
Germany Berlin 100
Germany Frankfurt 100
Germany Luxembourg 100
Netherlands Amsterdam 75
Spain Barcelona 93
The right result should be:
France Paris 85
Germany Berlin 100
Netherlands Amsterdam 75
Spain Barcelona 93
You can use row_number() :
select t.*
from (select t.*, row_number() over (partition by country order by city) as seq,
max(no_goods) over (partition by country) as max_good
from table t
) t
where seq = 1;
use aggregation functions min() for city and max() for no_of_goods.
select t1.country, t1.no_of_goods, min(t2.city) as city
from
(select country, max(no_of_goods) as no_of_goods from tableA
group by country) t1
left join tableA t2 on t2.no_of_goods = t1.no_of_goods and t1.country = t2.country
group by t1.country, t1.no_of_goods
see dbfiddle.
Basically, there are cities that have the same number of goods, but we only keep the first one in alphabetical order.
Based on your sample data, all cities in a country seem to have the same number_of_goods. If so, you can just use aggregation:
select c.country, min(c.city_name), max(number_of_goods)
from countries c join
goods g
on c.city_name = g.city_name
group by c.country;
I have a table City with two fields, CityCode and RegionCode
I have another table Code with two fields Code and CodeMeaning
I want to write a select statement that will display both cityCode, regionCode and their meanings for each city.
If i had to get one meaning from Code table i could do it with join but i don't know how to get values for both columns.
City Table Data
------------------------
CityCode RegionCode
34 53
41 43
Code Table Data
-----------------
Code Meaning
34 New York
41 Boston
53 North
43 South
Desired Output
------------------
CityCode RegionCode Region City
34 53 North New York
41 43 South Boston
Use two joins:
select cc.meaning as city, cr.meaning as region
from city c left join
code cc
on c.citycode = cc.code left join
code cr
on c.regioncode = cr.code
this is a bit poor db design but you can get the data with 2 joins to the codes table:
select c.*, c1.data as city, c2.data as region
from city_table c
join code_table c1 on c1.code = c.city_code
join code_table c2 on c2.code = c.region_code
-----------------------
country | city | ids
-----------------------
India Mumbai 1
India Chennai 2
India Kolkata 3
---------------------
USA New York 2
USA Utah 3
---------------------
I have given a sample from a table. From the table, I am trying to query all the countries without id 1. I wrote this(Country was not included in the Where condition since it needs to apply to all the countries of the table).
Select * from Countries
WHERE id<>1
I got this.
-----------------------
country | city | ids
-----------------------
India Chennai 2
India Kolkata 3
---------------------
USA New York 2
USA Utah 3
---------------------
But I need the output to contain only USA(which does not have id=1). Is there any workaround for this?
SELECT * from Countries WHERE country not in
(SELECT country from Countries WHERE id=1)
use NOT EXISTS
Select *
from Countries c
where not exists
(
select *
from Countries x
where x.country = c.country
and x.id = 1
)
You need to group by Country like below :
SELECT C.Country
FROM City
WHERE C.Country NOT IN
(SELECT country FROM City WHERE id=1)
SQL Fiddle Demo
OR
SELECT
C.Country
FROM
City C
GROUP BY C.Country
HAVING C.Country NOT IN
(
SELECT Country FROM City WHERE Id =1
)
SQL Fiddle Demo