Question

问题问

“编写查询以显示办公室所在的城市和国家/地区以及该位置的雇员人数。按雇员人数的降序对结果进行排序。”

到目前为止，我已经提出，

SELECT city, country, SELECT COUNT(city,country) 
FROM Offices
ORDER BY(SELECT COUNT(city,country) 
                FROM Offices)DESC;

但是我不能运行它。我认为我在SELECT COUNT部分中犯了一个错误。

employees表包含

employeeNumber
姓氏
名字
扩展名
电子邮件
报告给
jobTitle
officeCode

Office表包含

officeCode
城市
电话
addressLine1
addressLine2
状态
国家
postalCode
领土
officeLocation

有人知道我在做什么错吗？谢谢！抱歉，这是很多东西。

Answer 1

使用联接和计数

SELECT city, country,officeLocation, COUNT(e.employeeNumber) 
FROM Offices ofc join employees e on ofc.officeCode=e.officeCode
group by city, country,officeLocation

Answer 2

解决此问题的几种方法。使用左外部联接：（请确保在此处使用左外部而不是INNER JOIN，否则您只会获得有员工的位置。在您的情况下可能会起作用，但是如果某个位置没有现有员工怎么办？）

SELECT City, Country, COUNT(e.employeeNumber) AS EmployeeCount
FROM Offices o
LEFT OUTER JOIN Employees e
    ON e.OfficeCode = o.OfficeCode
GROUP BY City, Country
ORDER BY 3 DESC

或者您可以在选择语句中使用子查询：

SELECT City, Country,
    (SELECT COUNT(*) FROM Employees e WHERE o.OfficeCode = e.OfficeCode) AS EmployeeCount
FROM Offices o
ORDER BY 3 DESC

Answer 3

You can do it using a LEFT JOIN, GROUP BY and ORDER BY.
We need LEFT JOIN and GROUP BY to get the employee count and the ORDER BY to order the results in descending order of no of employees.

SELECT OfficeCode, City, Country, COUNT(E.employeeNumber) AS EmployeeCount
FROM Offices O
LEFT JOIN Employees E ON E.OfficeCode = E.OfficeCode
GROUP BY OfficeCode, City, Country
ORDER BY COUNT(E.employeeNumber) DESC

如何计算SQL中不同表中的雇员人数？

3 个答案: