SQL 统计某个国家的用户数
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Count number of users from a certain country
提问by Danilo
I have a table of users, and in this table I have a country field telling where these people are from (i.e. "Sweden", "Italy", ...). How can I do a SQL query to get something like:
我有一个用户表，在这个表中我有一个国家字段，告诉这些人来自哪里（即“瑞典”、“意大利”……）。我怎样才能做一个 SQL 查询来得到类似的东西：
Country Number
Sweden 10
Italy 50
... ...
Users select their countries from a list I give to them, but the list is really huge so it would be great to have a SQL query that can avoid using that list, that is look in the DB and give back only those countries which are in the database, because for example I have nobody from Barbados, even if I have that option in the country select field of the signup form :)
用户从我给他们的列表中选择他们的国家，但这个列表真的很大，所以如果有一个 SQL 查询可以避免使用该列表，那就是在数据库中查找并只返回那些在数据库，因为例如我没有来自巴巴多斯的人，即使我在注册表单的国家/地区选择字段中有该选项:)
Thanks in advance!
提前致谢！
回答by Wolph
This will give what you want. But you might want to cache the result of the query. With a lot of users it's quite a heavy query.
这会给你想要的。但您可能希望缓存查询结果。对于很多用户来说，这是一个非常繁重的查询。
SELECT
country,
COUNT(*)
FROM
users
GROUP BY
country
Perhaps a better idea is (assuming you don't need the counts) to do it like this:
也许更好的主意是（假设您不需要计数）这样做：
SELECT
DISTINCT country
FROM
users
回答by Raj More
If the name of the country is in the Users table, try something like this:
如果国家名称在用户表中，请尝试以下操作：
SELECT Country, COUNT (*) AS Number
FROM Users
GROUP BY Country
ORDER BY Country
If the name of the country is in the country table, then you will have to join
如果国家/地区名称在国家/地区表中，则您必须加入
SELECT Contries.CountryName, Count (*) AS Number
FROM Users
INNER JOIN Countries
ON Users.CountryId = Countries.CountryId
GROUP BY Countries.CountryName
ORDER BY Countries.CountryName
回答by AdaTheDev
Sounds like you want something like this...?
听起来你想要这样的东西......？
SELECT Country, COUNT(*) AS Number
FROM Users
GROUP BY Country
回答by marc_s
This is pretty straightforward:
这非常简单：
SELECT
Country, COUNT(*) AS 'Number'
FROM
YourTable
GROUP BY
Country
ORDER BY
Country
You just group your data by country and count the entries for each country.
您只需按国家/地区对数据进行分组并计算每个国家/地区的条目。
Or if you want them sorted by the number of visitors, use a different ORDER BY clause:
或者，如果您希望它们按访问者数量排序，请使用不同的 ORDER BY 子句：
SELECT
Country, COUNT(*) AS 'Number'
FROM
YourTable
GROUP BY
Country
ORDER BY
COUNT(*) DESC
回答by Alex Howansky
If you want the count per country:
如果您想要每个国家/地区的计数：
select country, count(*) from users group by country;
If you just want the possible values:
如果您只想要可能的值：
select distinct country from users;
