Sql查询帮助初学者

Question

嗨,我需要一个查询帮助(是的,我一直在尝试搜索,但找不到帮助我的东西)

我有两张桌子:

顾客

• CustomerID
• CountryID

国家

• CountryID
• Country

我如何编写查询以获得如下结果:

CountryID, Country, NumberOfOccurancesOfThisCountryInTheCustomerTable

真的很感激帮助!

Answer 1

试试这个:

SELECT CountryID, Country,
  COUNT(Customer.CustomerID) AS NumberOfOccurancesOfThisCountryInTheCustomerTable
FROM Country LEFT JOIN
     Customer ON Country.CountryID = Customer.CountryID
GROUP BY Country.CountryID, Country.Country

编辑:使用LEFT JOINvs. INNER JOIN包括Country记录为零的Customer记录(感谢Mark Ba​​nnister).